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  • DEEP DIVE MVVM at #MIX11

    - by Laurent Bugnion
    The public (you!) has spoken, and “Deep Dive MVVM” was selected (along with 11 other open call talks) out of 217 proposals. There were 17’000 votes! These are pretty amazing numbers, and believe me when I tell you that I still didn’t completely realize what just happened! I want to really underline the outstanding quality of many of the talks that were proposed. I decided not to reveal my votes, because I just know too many of the candidates and I had only 10 votes but let’s just say that some of my favorites were picked, and some were not, and I really wish that I can see them all either at MIX or in another conference. I already started putting down ideas for the talk (not too many, because I didn’t want to jinx it) and it should be a really great session. We will, as the title shows, dive deep into the subtleties of MVVM, and explore some techniques that allow to overcome some of the hurdles presented by this pattern. This session will be shaped by many emails that I received over the past year, since “Understanding the MVVM pattern” was presented, and offered, for many, a first look into Model-View-ViewModel. So now’s the chance, comment and let me know what topics you would like to discuss. If you had not done so before, go ahead and watch last year’s session, it will be a great preparation. Let’s talk real life development, let’s explore the problems and find solutions. I already have a nice collection of emails asking questions around MVVM and my goal is to answer as many as I can. Leave a comment and I will do my best to answer these as well. The date/time was not announced yet, so watch this space for details. I am really looking forward to seeing many of you in Las Vegas, and for those who cannot make it, don’t worry, all the sessions will be published in video by the amazing MIX team a few hours after the session actually takes place. Thanks for your confidence and in the meantime, Happy Coding! Laurent Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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  • The Other "C" in CRM

    - by Brian Dayton
    Folks who know me know that I rarely, if ever, talk politics. And I never talk politicians. Having grown up in a household with one parent leaning left and the other leaning to the right it was the best way to keep the peace. This isn't about politics. It's about "constituents" and the need to improve the services and service levels for people--at the city, county, state/province, etc. level all the way up to national governments. As a citizen and tax payer it's also important to me that these services be provided at a reasonable cost. If there's a better and more efficient way to do something then it's my hope that a public sector organization takes advantage of technology the same way private sector companies do. Social services organizations have a complex job. They provide the services that people need, from healthcare and children's assistance to helping people find jobs. But many of these organizations are still managing these processes manually or outdated, home-grown applications that could have been written up to 30 years ago. A lot has changed in technology. On the (this is as political as I'm going to get) political front, stakeholders like you and me are expecting greater transparency on where and how funds are spent. I'll admit that most of the time, when I think about CRM systems, I think about my experience as a customer of my bank, utilities company or cable operator. But now that I'm older, have children and a house--I find myself interacting more and more with agencies and services organizations. My experiences are sometimes good and sometimes not so good. Along those lines, last week's announcement of Siebel CRM 8.2 for Public Sector caught my eye. You may not work in the public sector, but you are a constituent of some--actually a lot--of public sector organizations. I don't know which CRM systems city and county utilize but I'm going to start paying closer attention.

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  • Windows 7 not booting after installing Ubuntu 12.10

    - by Imran Choudhry
    I have Samsung sf511 with Windows 7 Home preinstalled. I installed Ubuntu 12.10 last night. First I mounted downloaded ubuntu 12.10 iso on a DVD from Windows 7, then I restarted, changed the boot option to DVD and let the Ubuntu DVD run. I selected "Install ubuntu alongside windows 7". In the next step I allocated the diskspace . Ubuntu installed perfectly and it ranned OK. I spent a good time exploring Ubuntu. When I restarted to start my work on Windows again and selected Windows 7 to boot, it showed blue screen after booting up (after logging in). I tried restarting several times but the same blue screen keep showing at the same point of bootup. I also restored windows to an earlier time. Left with no option I booted from Samsung provided windows recovery option. The recovery process ran fine but when it restarted to boot Windows for the first time all I see is a black screen. Nothing happens. It switches between dark command promt screen to a pitch black screen as if it's rebooting after every 10 seconds or so. The laptop can be booted from the DVD Drive or USB drive but is not booting from Harddisk. What should I do in order to use both Windows 7 and Ubuntu?

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  • SQL SERVER – Download Free eBook – Introducing Microsoft SQL Server 2012

    - by pinaldave
    Database Administration and Business Intelligence is indeed very key area of the SQL Server. My very good friend Ross Mistry and Stacia Misner has recently wrote book which is for SQL Server 2012. The best part of the book is it is totally FREE! Well, this book assumes that you have certain level of SQL Server Administration as well Business Intelligence understanding. So if you are absolutely beginner I suggest you read other books of Ross as well attend Pluralsight course of Stacia Misner. Personally I read this book in last 10 days and I find it very easy to read and very comprehensive as well. Part I Database Administration (by Ross Mistry) 1. SQL Server 2012 Editions and Engine Enhancements 2. High-Availability and Disaster-Recovery Enhancements 3. Performance and Scalability 4. Security Enhancements 5. Programmability and Beyond-Relational Enhancements Part II Business Intelligence Development (by Stacia Misner) 6. Integration Services 7. Data Quality Services 8. Master Data Services 9. Analysis Services and PowerPivot 10. Reporting Services Here are various versions of the eBook. PDF ePub Mobi Amazon Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Database, PostADay, SQL, SQL Authority, SQL Download, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • New site – and a special offer

    - by Red Gate Software BI Tools Team
    SSAS Compare has a brand new website! The old page was thrown together in the way that most Red Gate labs sites tend to be — as experimental sites for experimental products. We’ve been developing SSAS Compare for a while now, so we decided it was time for something a bit prettier. The new site is mostly the work of Andrew, our marketing manager, who has all sorts of opinions about websites. One of the opinions Andrew has is that his photo should be on every site on the internet, or at least every Red Gate site on the internet, and that’s why his handsome visage now appears on the SSAS Compare page. Well, that isn’t quite true. According to Andrew, people download more software when they have photos of human beings to look at. We want as many people to try SSAS Compare as possible, so we got the team together for an intimate photoshoot directed by Red Gate’s resident recorder of light, Dom Reed (aka Mr Flibble). The photo will appear on the site as soon as Dom is finished photoshopping us into something more palatable, which is a big job. Until then, you’ll have to put up with Andrew. We’ve also used the new site to announce a special offer. Right now, SSAS Compare is still a free beta, but by signing up to our Early Access Program, you’ll get a 20% discount when we release SSAS Compare as a fully-fledged product. We’ll use your email address to send you news and updates about business intelligence tools from Red Gate (and nothing else). If that sounds good to you, go to the SSAS Compare site to sign up. By the way, the BI Tools team wasn’t the only thing Dom photographed last week. Remember Noemi’s blog about the flamenco dance? We’ll be at SQL Saturday in our home town of Cambridge this Saturday (8th September), handing out flyers of a distinctly Mediterranean flavour. If you’re attending, be sure to say hello!

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  • I can't add PPA repository behind the proxy (with @ in the username)

    - by kenorb
    I'm trying to add the ppa repository (as a root) with the following command: export HTTP_PROXY="http://[email protected]:[email protected]:8080" add-apt-repository ppa:nilarimogard/webupd8 Traceback (most recent call last): File "/usr/bin/add-apt-repository", line 125, in <module> ppa_info = get_ppa_info_from_lp(user, ppa_name) File "/usr/lib/python2.7/dist-packages/softwareproperties/ppa.py", line 84, in get_ppa_info_from_lp curl.perform() pycurl.error: (56, 'Received HTTP code 407 from proxy after CONNECT') Unfortunately it doesn't work. Looks like curl is connecting to the proxy, but the proxy says that Authentication is Required. I've tried with .curlrc, http_proxy env instead, but it doesn't work. strace -e network,write -s1000 add-apt-repository ppa:nilarimogard/webupd8 socket(PF_INET6, SOCK_DGRAM, IPPROTO_IP) = 4 socket(PF_INET, SOCK_STREAM, IPPROTO_TCP) = 4 connect(4, {sa_family=AF_INET, sin_port=htons(8080), sin_addr=inet_addr("165.x.x.232")}, 16) = -1 EINPROGRESS (Operation now in progress) getsockopt(4, SOL_SOCKET, SO_ERROR, [0], [4]) = 0 getpeername(4, {sa_family=AF_INET, sin_port=htons(8080), sin_addr=inet_addr("165.x.x.232")}, [16]) = 0 getsockname(4, {sa_family=AF_INET, sin_port=htons(46025), sin_addr=inet_addr("161.20.75.220")}, [16]) = 0 sendto(4, "CONNECT launchpad.net:443 HTTP/1.1\r\nHost: launchpad.net:443\r\nUser-Agent: PycURL/7.22.0\r\nProxy-Connection: Keep-Alive\r\nAccept: application/json\r\n\r\n", 146, MSG_NOSIGNAL, NULL, 0) = 146 recvfrom(4, "HTTP/1.1 407 Proxy Authentication Required\r\nProxy-Authenticate: BASIC realm=\"proxy\"\r\nCache-Control: no-cache\r\nPragma: no-cache\r\nContent-Type: text/html; charset=utf-8\r\nProxy-Connection: close\r\nSet-Cookie: BCSI-CS-91b9906520151dad=2; Path=/\r\nConnection: close\ Maybe it's because there is @ sign in the username? Wget works with proxy fine. Related: How do I add a repository from behind a proxy? Environment Ubuntu 12.04 curl 7.22.0 (x86_64-pc-linux-gnu) libcurl/7.22.0 OpenSSL/1.0.1 zlib/1.2.3.4 libidn/1.23 librtmp/2.3 curl Features: GSS-Negotiate IDN IPv6 Largefile NTLM NTLM_WB SSL libz TLS-SRP

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  • Will my system fsck when I reboot?

    - by Tom Newton
    ...and how do I find out? Say I am about to reboot a server. I would like to minimize downtime, so thinking about wrapping reboot in an alias that says "hang on buddy, you're going to hit a fsck on boot". Next question.. what's the best way to say "lets do it next time?" set the last check date? I know tune2fs can set a bunch of parameters, but how would I get em?

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  • Nginx + CodeIgniter + Invision power board rewrite rule probem.

    - by Ufuk
    Hello, I have a setup where I have a folder structre like: / /application /system /forum index.php My ngix configuration: if (!-f $request_filename) { rewrite ^/(.*)$ /index.php/$1 last; } location ~ /index.php { fastcgi_pass 127.0.0.1:9000; fastcgi_index index.php; include /usr/local/nginx/conf/fastcgi_params; fastcgi_param SCRIPT_FILENAME /var/www/vhosts/mydomain.com/httpdocs/index.php; } This setup works correctly and redirects urls to correct controller of codeigniter yet it does also forward www.mydomain.com/forum to codeigniter, which eventually shows a 404 page of CodeIgniter. Does anyone know the correct configuration for my setups? Thank you.

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  • Snort: not logging anything

    - by ethrbunny
    My site seems to be the target of quite a bit of probing over the last few months. In an attempt to get a better handle on this I installed SNORT on one of the machines that has external exposure. Something must not be installed correctly as I see lots of probing in /var/log/messages but snort isn't logging anything. System: CentOS 6.2 (32 bit) Snort: (latest build and rules) Snort configured from this v excellent site: http://nachum234.no-ip.org/security/snort/001-snort-installation-on-centos-6-2/ snort running as daemon: /usr/local/bin/snort -d -D -i bond0 -u snort -g snort -c /etc/snort.d/snort.conf -l /var/log/snort The snort.log file is empty despite hundreds (or more) failed login attempts from individual IP addresses. Maybe Im missing the purpose of SNORT? I was hoping it would log this sort of info.

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  • How to penetrate the QA industry after layoffs, next steps...

    - by Erik
    Briefly, my background is in manual black box testing of websites and applications within the Agile/waterfall context. Over the past four years I was a member of two web development firms' small QA teams dedicated to testing the deployment of websites for national/international non profits, governmental organizations, and for profit business, to name a few: -Brookings Institution -Senate -Tyco Electronics -Blue Cross/Blue Shield -National Geographic -Discover Channel I have a very strong understanding of the: -SDLC -STLC of bugs and website deployment/development -Use Case & Test Case development In March of this year, my last firm downsized and lost my job as a QA tester. I have been networking and doing a very detailed job search, but have had a very difficult time getting my next job within the QA industry, even with my background as a manual black box QA tester in the website development context. My direct question to all of you: What are some ways I can be more competitive and get hired? Options that could get me competitive: Should I go back to school and learn some more 'hard' skills in website development and client side technologies, e.g.: -HTML -CSS -JavaScript Learn programming: -PHP -C# -Ruby -SQL -Python -Perl -?? Get Certified as a QA Tester, there are a countless numbers of programs to become a Certified Tester. Most, if not all jobs, being advertised now require Automated Testing experience, in: -QTP -Loadrunner -Selenium -ETC. Should I learn, Automated testing skills, via a paid course, or teach myself? --Learn scripting languages to understand the automated testing process better? Become a Certified "Project Management Professional" (PMP) to prove to hiring managers that I 'get' the project development life cycle? At the end of the day I need to be competitive and get hired as a QA tester and want to build upon my skills within the QA web development field. How should I do this, without reinventing the wheel? Any help in this regard would be fabulous. Thanks! .erik

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  • Should we always prefer OpenGL ES version 2 over version 1.x

    - by Shivan Dragon
    OpengGL ES version 2 goes a long way into changing the development paradigm that was established with OpenGL ES 1.x. You have shaders which you can chain together to apply varios effects/transforms to your elements, the projection and transformation matrices work completly different etc. I've seen a lot of online tutorials and blogs that simply say "ditch version 1.x, use version 2, that's the way to go". Even on Android's documentation it sais to "use version 2 as it may prove faster than 1.x". Now, I've also read a book on OpenGL ES (which was rather good, but I'm not gonna mention here because I don't want to give the impression that I'm trying to make hidden publicity). The guy there treated only OpenGL ES 1.x for 80% of the book, and then at the end only listed the differences in version 2 and said something like "if OpenGL ES 1 does what you need, there's no need to switch to version 2, as it's only gonna over complicate your code. Version 2 was changed a lot to facillitate newer, fancier stuff, but if you don't need it, version 1.x is fine". My question is then, is the last statement right? Should I always use Open GL ES version 1.x if I don't need version 2 only stuff? I'd sure like to do that, because I find coding in version 1.x A LOT simpler than version 2 but I'm afraid that my apps might get obsolete faster for using an older version.

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  • When I try to click and launch some of the links set to open in new window, it is being treated as a pop-up window [migrated]

    - by Test Developer
    For the past few days, we are facing issue with the chrome browser behavior. This is related to opening links set to open in new tab/window. The details are as follow: I have a collection of links and each link points to different resource to be opened in a new tab/window. The code is as follow: <a class="cssClass" rid="1114931" href="http://www.domain.com/resources/abc.html" title="Link1" tabindex="4">Link 1</a> And there are few checks/filters over accessing the resources which have been implemented as onClick handler over the links. In case any of the validations fails, the onClick handler returns false and the default behavior of the link does not happens i.e. links does not get open. One of such (last) checks includes AJAX call in sync mode. The code is as follow: var link_clickHandler = function(evt/* Event */) { var objTarget = jQuery(evt.target); if(check1) { return false; } else if(check2) { return false; } else if(check3) { var blnRetVal = false; jQuery.ajax( { "async" : false, "type" : "GET", "contentType" : "application/json; charset=utf-8", "url" : "index.php", "data" : 'resourceid=' + intResourceId, "dataType" : "json", "forceData" : true, "success" : function(data) { if(check1) { blnRetVal = true; } } "error" : function(error) { } } ); return blnRetVal; } }; jQuery("a.cssClass").live("click", link_clickHandler); ISSUE: The issue is that Chrome is behaving very weirdly manner. In case all of the checks are passed and onClick handler returns true, sometimes the resource get opened in a new tab/window and sometimes it get opened as a pop-up (which should never). Tried to capture any pattern but could not succeed. Any solution or even helping in understanding behavior would be really appreciated.

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  • MSCC: Purpose and benefits of Version Control Systems (VCS)

    Unfortunately, there was no monthly meetup during May. Which means that it was even more important and interesting to go forward with a great topic for this month. Earlier this year I already spoke to Nayar Joolfoo about doing a presentation on version control systems (VCS), and he gladly agreed since then. It was just about finding the right date for the action. Furthermore, it was also a great coincidence that Avinash Meetoo announced on social media networks that Knowledge 7 is about to have a new training on "Effective git" - which correlates to a book title Avinash is currently working on - all the best with your approach on this and reach out to our MSCC craftsmen for recessions. Once again a big Thank you to Orange Ebene Accelerator on providing the venue for us, and the MSCC members involved on securing the time slot for our event. Unfortunately, it's kind of tough to get an early confirmation for our meetups these days. I'll keep you posted on that one as there are some interesting and exciting options coming up soon. Okay, let's talk about the meeting and version control systems again. As usual, I'm going to put my first impression of the meetup: "Absolutely great topic, questions and discussions on version control systems, like git or VSO. I was also highly pleased by the number of first timers and female IT geeks. Hopefully, we will be able to keep this trend for future get-togethers." And I really have to emphasise the amount of fresh blood coming to our gathering. Also, during the initial phase it was surprising to see that exactly those first-timers, most of them students at various campuses here on the island, had absolutely no idea about version control systems. More about further down... Reactions of other attendees If I counted correctly, we had a total of 17 attendees this month, and I'd like to give you feedback from some of them: "Inspiring. Helped me understand more about GIT." -- Sean on event comments "Joined the meetup today with literally no idea what is a version control system. I have several reasons why I should be starting to use VCS as from NOW in my projects. Thanks Nayar, Jochen and other participants :)" -- Yudish on event comments "Was present today and I'm very satisfied.I was not aware if there was a such tool like git available. Thanks to those who contributed for this meetup.It was great. Learned a lot from this meetup!!" -- Leonardo on event comments "Seriously, I can see how it’s going to ease my task and help me save time. Gone are the issues with files backups.  And since I’ll be doing my dissertation this year, using Git would help me a lot for my backups and I’m grateful to Nayar for the great explanation." -- Swan-Iyah on MSCC meetup : Version Controls Hopefully, I'll be able to get some other sources - personal blogs preferred - on our meeting. Geeks, thank you so much for those encouraging comments. It's really great to experience that we, all members of the MSCC, are doing the right thing to get more IT information out, and to help each other to improve and evolve in our professional careers. Our agenda of the day Honestly, we had a bumpy start... First, I was battling a little bit with the movable room divider in order to maximize the space. I mean, we had 24 RSVPs and usually there might additional people coming along. Then, for what ever reason, we were facing power outages - actually twice in short periods. Not too good for the projector after all, but hey it went smooth for the rest of the time being. And last but not least... our first speaker Nayar got stuck somewhere on the road. ;-) Anyway, not a real show-stopper and we used the time until Nayar's arrival to introduce ourselves a little bit. It is always important for me to get to know the "newbies" a little bit, and as a result we had lots of students of university - first year, second year and recent graduates - among them. Surprisingly, none of them was ever in contact with version control systems at all. I mean, this is a shocking discovery! Similar to the ability of touch-typing I'd say that being able to use (and master) any kind of version control system is compulsory in any job in the IT industry. Seriously, I'm wondering what is being taught during the classes on the campus. All of them have to work on semester assessments or final projects, even in small teams of 2-4 people. That's the perfect occasion to get started with VCS. Already in this phase, we had great input from more experienced VCS users, like Sean, Avinash and myself. git - a modern approach to VCS - Nayar What a tour! Nayar gave us the full round of git from start to finish, even touching some more advanced techniques. First, he started to explain about the importance of version control systems as an essential tool for software developers, even working alone on a project, and the ability to have a kind of "time machine" that allows you to inspect and revert to a previous version of source code at any time. Then he showed how easy it is to install git on an Ubuntu based system but also mentioned that git is literally available for any operating system, like Windows, Mac OS X and of course other Linux distributions. Next, he showed us how to set the initial configuration values of user name and email address which simplifies the daily usage of the git client while working with your repositories. Then he initialised and added a new repository for some local development of a blogging software. All commands were done using the command line interface (CLI) so that they can be repeated on any system as reference. The syntax and the procedure is always the same, and Nayar clearly mentioned this to the attendees. Now, having a git repository in place it was about time to work on some "important" changes on the blogging software - just for the sake of demonstrating the ease of use and power of git. One interesting question came very early: "How many commands do we have to learn? It looks quite difficult at the moment" - Well, rest assured that during daily development circles you will need less than 10 git commands on a regular base: git add, commit, push, pull, checkout, and merge And Nayar demo'd all of them. Much to the delight of everyone he also showed gitk which is the git repository browser. It's an UI tool to display changes in a repository or a selected set of commits. This includes visualizing the commit graph, showing information related to each commit, and the files in the trees of each revision. Using gitk to display and browse information of a local git repository And last but not least, we took advantage of the internet connectivity and reached out to various online portals offering git hosting for free. Nayar showed us how to push the local repository into a remote system on github. Showing the web-based git browser and history handling, and then also explained and demo'd on how to connect to existing online repositories in order to get access to either your own source code or other people's open source projects. Next to github, we also spoke about bitbucket and gitlab as potential online platforms for your projects. Have a look at the conditions and details about their free service packages and what you can get additionally as a paying customer. Usually, you already get a lot of services for up to five users for free but there might be other important aspects that might have an impact on your decision. Anyways, moving git-based repositories between systems is a piece of cake, and changing online platforms is possible at any stage of your development. Visual Studio Online (VSO) - Jochen Well, Nayar literally covered all elements of working with git during his session, including the use of external online platforms. So, what would be the advantage of talking about Visual Studio Online (VSO)? First of all, VSO is "just another" online platform for hosting and managing git repositories on remote systems, equivalent to github, bitbucket, or any other web site. At the moment (of writing), Microsoft also provides a free package of up to five users / developers on a git repository but there is more in that package. Of course, it is related to software development on the Windows systems and the bonds are tightened towards the use of Visual Studio but out of experience you are absolutely not restricted to that. Connecting a Linux or Mac OS X machine with a git client or an integrated development environment (IDE) like Eclipse or Xcode works as smooth as expected. So, why should one opt in for VSO? Well, one of the main aspects that I would like to mention here is that VSO integrates the Application Life Cycle Methodology (ALM) of Microsoft in their platform. Meaning that you get agile project management with Backlogs, Sprints, Burn-down charts as well as the ability to track tasks, bug reports and work items next to collaborative team chats. It's the whole package of agile development you'll get. And, something I mentioned briefly during the begin of our meeting, VSO gives you the possibility of an automated continuous integrated (CI) process which builds and can run tests of your source code after each commit of changes. Having a proper CI strategy is also part of the Clean Code Developer practices - on Level Green actually -, and not only simplifies your life as a software developer but also reduces the sources of potential errors. Seamless integration and automated deployment between Microsoft Azure Web Sites and git repository But my favourite feature is the seamless continuous deployment to Microsoft Azure. Especially, while working on web projects it's absolutely astounishing that as soon as you commit your chances it just takes a couple of seconds until your modifications are deployed and available on your Azure-hosted web sites. Upcoming Events and networking Due to the adjusted times, everybody was kind of hungry and we didn't follow up on networking or upcoming events - very unfortunate to my opinion and this will have an impact on future planning of our meetups. Because I rather would like to see more conversations during and at the end of our meetings than everyone just packing their laptops, bags and accessories and rush off to grab some food. I was hoping to get some information regarding this year's Code Challenge - supposedly to be organised during July? Maybe someone could leave a comment on that - but I couldn't get any updates. Well, I'll keep digging... In case that you would like to get more into git and how to use it effectively, please check out Knowledge 7's upcoming course on "Effective git". Thanks Avinash for your vital input into today's conversation and I'm looking forward to get a grip on your book title very soon. My resume of the day Do not work in IT without any kind of version control system! Seriously, without a VCS in place you're doing it wrong. It's like driving a car without seat belts attached or riding your bike without safety helmet. You don't do that! End of discussion. ;-) Nowadays, having access to free (as in cost) tools to install on your machine and numerous online platforms to host your source code for free for up to five users it's a no-brainer to get yourself familiar with VCS. Today's sessions gave a good overview on how to start using git and how to connect to various remote services like github or VSO.

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  • hp smart array lock up code 0x15, what is that? (or where can I get a list of descriptions of HP smart array controller lock up codes)

    - by user47650
    Hi, I've had a couple of Dl180 6g boxes hung over the last week, each have a P410 smart array controller. upon reboot the server has indicated that a controller failure event occurred and the previous lock up code was 0x15 - the server rebooted without issue. However there was nothing in the IML log, but the ADU report provided the following; Trap Address High Or Post Results Lockup Reason Or Post Error RIS Updates Or Post Error Detail Firmware Version Trap Address Low 0x8087 0x0015 0x0000033e 0x015e 0xd65c any suggestions on what that code is, my google fu failed. And hp support have not responded with any detail as yet.

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  • Cant add network printer with system-config-printer package

    - by Erick David Ruiz Coronel
    Hello im new here and I dont know if im doing it right but I hope yes. I have a printer conected to a windows 8 machine, also I had ubuntu 13.04 and it worked fine when I printed from linux to windows but when I upgraded to 13.10 my printer didnt worked, I removed it thinking that would fix it but when I tryed to add the printer again I couldnt, I reinstalled cups and the system-config-printer-gnome package but didnt worked. Here is the terminal log : erick@Tauro:~$ system-config-printer Caught non-fatal exception. Traceback: File "/usr/share/system-config-printer/probe_printer.py", line 255, in _do_find fn () File "/usr/share/system-config-printer/probe_printer.py", line 367, in _probe_hplip stderr=null) File "/usr/lib/python2.7/subprocess.py", line 709, in init errread, errwrite) File "/usr/lib/python2.7/subprocess.py", line 1326, in _execute_child raise child_exception OSError: [Errno 2] No existe el archivo o el directorio Continuing anyway.. Traceback (most recent call last): File "/usr/share/system-config-printer/newprinter.py", line 912, in on_btnNPForward_clicked self.nextNPTab() File "/usr/share/system-config-printer/newprinter.py", line 1064, in nextNPTab stderr=file("/dev/null")) File "/usr/lib/python2.7/subprocess.py", line 709, in init errread, errwrite) File "/usr/lib/python2.7/subprocess.py", line 1326, in _execute_child raise child_exception OSError: [Errno 2] No existe el archivo o el directorio Any suggestion please? C:

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  • Collaborate 2010 Recap: A lot of Excitement for Oracle Content Management 11g

    - by [email protected]
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} Collaborate brought me to Las Vegas last week and what a week it was.  Each day was jam packed with Oracle Content Management sessions, and almost every session I attended was full.  Across the 35+ sessions that were given by my Oracle peers, Oracle partners, and Oracle customers, the majority of the discussion and questions that were asked had to do with the release of Oracle Content Management 11g.  Just to bring everyone up-to-speed, the first wave of Oracle Content Management 11g releases happened this past January as Oracle Imaging & Process Management and Oracle Information Rights Management went GA.  The next wave, which should be released soon, includes Oracle Universal Content Management and Oracle Universal Records Management. Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} Andy MacMillan and Roel Stalman kicked off these discussions last Monday, as they presented Oracle Content Management's product strategy and roadmap.  It seemed that the attendees liked what they heard regarding the strategy and future direction, but the question that seems to always come up after roadmap presentations is "when will the product be released"?  This is a question that none of us have the power to answer, but soon customers will be able to enjoy these new product capabilities: Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} Unified content repository across ECMCentralized installation, access, administration & monitoringCertified application integrations with solution templatesOpen Web Content Management Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} Stay tuned for more news about the release of Oracle Universal Content Management and Oracle Records Management.  There are a lot of new assets currently being built that will help get everyone up-to-speed quickly. Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} Outside of the sessions that were presented, there were a lot of other activities that took place at Collaborate.  The Enterprise 2.0 solutions demo pod was busy, and attendees were anxious to see demonstrations of Oracle's end-to-end document imaging solution, WebCenter Spaces, and web site creation using Oracle Universal Content Management.   I also want to thank our partners (Fishbowl Solutions, Redstone Content Solutions, Bezzotech, Team Informatics, and DTI) for their efforts in creating detailed, insightful presentations.  Also, special thanks are in order to Thomas Feldmeier and Markus Neubauer of Silbury IT-Beratung GmbH for their participation.  It seems that Thomas and Markus were doomed to be stranded in Frankfurt after the Icelandic ash storm.  They couldn't get a flight out of their native Germany, and with fear that they would miss Collaborate, they rented a car and drove to Rome - some 800 miles (1,200 kilometers).  Anyway, they made it safe and sound to Las Vegas, and although probably a bit tired, they gave 2 Oracle Content Management presentations.  Talk about commitment. Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} Finally, a very special thanks to Al Hoof and Dave Chaffee of the Oracle Content Management Special Interest Group (SIG).  Al and Dave did most of the heavy lifting for Collaborate, including the coordination of all the sessions.  The Independent Oracle Users Group presented Al with the Chris Wooldridge award, recognizing him as the volunteer of the year.  Here is Al with his award: Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} I hope to see you next year at Collaborate as the show returns to Orlando.

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  • Fix: Azure Disabled over 49 cents? Beware of using a Java Virtual Machine on Microsoft Azure

    - by Ken Cox [MVP]
    I love my MSDN Azure account. I can spin up a demo/dev app or VM in seconds. In fact, it is so easy to create a virtual machine that Azure shut down my whole account! Last night I spun up a Java Virtual Machine to play with some Android stuff. My mistake was that I didn’t read the Virtual Machine pricing warning: “I have a MSDN Azure Benefit subscription. Can I use my monthly Azure credits to purchase Oracle software?” “No, Azure credits in our MSDN offers are not applicable to Oracle software. In order to purchase Oracle software in the MSDN Azure Benefit subscription, customers need to turn off their {0} spending limit and pay at the regular pay-as-you-go rate. Otherwise, Oracle usage will hit the {1} spending limit and the subscription will be immediately disabled.”  Immediately disabled? Yup. Everything connected to the subscription was shut off, deallocated, rendered useless - even the free Web sites and the free Sendgrid email service.  The fix? I had to remove the spending limit from my account so I could pay $0.49 (49 cents) for the JVM usage. I still had $134.10 in credits remaining for regular usage with 6 days left in the billing month.  Now the restoration/clean-up begins… figuring out how to get the web sites and services back online.  To me, the preferable way would be for Azure to warn me when setting up a JVM that I had no way of paying for the service. In the alternative, shut down just the offending services – the ones that can’t be covered by the regular credits. What a mess.

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  • Metro: Understanding Observables

    - by Stephen.Walther
    The goal of this blog entry is to describe how the Observer Pattern is implemented in the WinJS library. You learn how to create observable objects which trigger notifications automatically when their properties are changed. Observables enable you to keep your user interface and your application data in sync. For example, by taking advantage of observables, you can update your user interface automatically whenever the properties of a product change. Observables are the foundation of declarative binding in the WinJS library. The WinJS library is not the first JavaScript library to include support for observables. For example, both the KnockoutJS library and the Microsoft Ajax Library (now part of the Ajax Control Toolkit) support observables. Creating an Observable Imagine that I have created a product object like this: var product = { name: "Milk", description: "Something to drink", price: 12.33 }; Nothing very exciting about this product. It has three properties named name, description, and price. Now, imagine that I want to be notified automatically whenever any of these properties are changed. In that case, I can create an observable product from my product object like this: var observableProduct = WinJS.Binding.as(product); This line of code creates a new JavaScript object named observableProduct from the existing JavaScript object named product. This new object also has a name, description, and price property. However, unlike the properties of the original product object, the properties of the observable product object trigger notifications when the properties are changed. Each of the properties of the new observable product object has been changed into accessor properties which have both a getter and a setter. For example, the observable product price property looks something like this: price: { get: function () { return this.getProperty(“price”); } set: function (value) { this.setProperty(“price”, value); } } When you read the price property then the getProperty() method is called and when you set the price property then the setProperty() method is called. The getProperty() and setProperty() methods are methods of the observable product object. The observable product object supports the following methods and properties: · addProperty(name, value) – Adds a new property to an observable and notifies any listeners. · backingData – An object which represents the value of each property. · bind(name, action) – Enables you to execute a function when a property changes. · getProperty(name) – Returns the value of a property using the string name of the property. · notify(name, newValue, oldValue) – A private method which executes each function in the _listeners array. · removeProperty(name) – Removes a property and notifies any listeners. · setProperty(name, value) – Updates a property and notifies any listeners. · unbind(name, action) – Enables you to stop executing a function in response to a property change. · updateProperty(name, value) – Updates a property and notifies any listeners. So when you create an observable, you get a new object with the same properties as an existing object. However, when you modify the properties of an observable object, then you can notify any listeners of the observable that the value of a particular property has changed automatically. Imagine that you change the value of the price property like this: observableProduct.price = 2.99; In that case, the following sequence of events is triggered: 1. The price setter calls the setProperty(“price”, 2.99) method 2. The setProperty() method updates the value of the backingData.price property and calls the notify() method 3. The notify() method executes each function in the collection of listeners associated with the price property Creating Observable Listeners If you want to be notified when a property of an observable object is changed, then you need to register a listener. You register a listener by using the bind() method like this: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price observableProduct.price = 2.99; } }; app.start(); })(); In the code above, the bind() method is used to associate the price property with a function. When the price property is changed, the function logs the new value of the price property to the Visual Studio JavaScript console. The price property is associated with the function using the following line of code: // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); Coalescing Notifications If you make multiple changes to a property – one change immediately following another – then separate notifications won’t be sent. Instead, any listeners are notified only once. The notifications are coalesced into a single notification. For example, in the following code, the product price property is updated three times. However, only one message is written to the JavaScript console. Only the last value assigned to the price property is written to the JavaScript Console window: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price observableProduct.price = 3.99; observableProduct.price = 2.99; observableProduct.price = 1.99; Only the last value assigned to price, the value 1.99, appears in the console: If there is a time delay between changes to a property then changes result in different notifications. For example, the following code updates the price property every second: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Add 1 to price every second window.setInterval(function () { observableProduct.price += 1; }, 1000); In this case, separate notification messages are logged to the JavaScript Console window: If you need to prevent multiple notifications from being coalesced into one then you can take advantage of promises. I discussed WinJS promises in a previous blog entry: http://stephenwalther.com/blog/archive/2012/02/22/windows-web-applications-promises.aspx Because the updateProperty() method returns a promise, you can create different notifications for each change in a property by using the following code: // Change the price observableProduct.updateProperty("price", 3.99) .then(function () { observableProduct.updateProperty("price", 2.99) .then(function () { observableProduct.updateProperty("price", 1.99); }); }); In this case, even though the price is immediately changed from 3.99 to 2.99 to 1.99, separate notifications for each new value of the price property are sent. Bypassing Notifications Normally, if a property of an observable object has listeners and you change the property then the listeners are notified. However, there are certain situations in which you might want to bypass notification. In other words, you might need to change a property value silently without triggering any functions registered for notification. If you want to change a property without triggering notifications then you should change the property by using the backingData property. The following code illustrates how you can change the price property silently: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price silently observableProduct.backingData.price = 5.99; console.log(observableProduct.price); // Writes 5.99 The price is changed to the value 5.99 by changing the value of backingData.price. Because the observableProduct.price property is not set directly, any listeners associated with the price property are not notified. When you change the value of a property by using the backingData property, the change in the property happens synchronously. However, when you change the value of an observable property directly, the change is always made asynchronously. Summary The goal of this blog entry was to describe observables. In particular, we discussed how to create observables from existing JavaScript objects and bind functions to observable properties. You also learned how notifications are coalesced (and ways to prevent this coalescing). Finally, we discussed how you can use the backingData property to update an observable property without triggering notifications. In the next blog entry, we’ll see how observables are used with declarative binding to display the values of properties in an HTML document.

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  • The Social Business Thought Leaders - John Hagel

    - by kellsey.ruppel
    While many European economies are on the brink of a recession between increasing taxation and mounting loss of jobs and bankruptcy filing rates, there's an understandable risk of losing sight of the deeper forces at play. Yet instead of surrendering to uncertainty and trying to survive in the short term, many organizations are feeling the urge to be better prepared to thrive in these complex times by developing a more articulated long term understanding of both the opportunities / challenges ahead. For example: What long-term economic, technological and societal changes are rolling out? Which foundational dynamics will affect our companies' performance, productivity, competition, and innovative potential in the upcoming decades? How will digital infrastructure change our business landscape? What kind of capabilities will be key to compete in a market shaped by growing turbulence, unpredictability and volatility? Breaking out from a strictly cyclical thinking, studies such as the Shift Index by John Hagel, Co-Chairman of the Center for the Edge at Deloitte & Touche (See Measuring the forces of long-term change - The 2009 Shift Index), depict a worrying performance challenge that affected every industry in the entire US economy over the last 45 years. Amidst a more than doubled competitive intensity of the market, and even with an improved labor productivity, the actual performance of US firms has consistently fallen to 25% of what it was in 1965. Most of this reported value is shifting from institutions and organizations to individuals, whether they are customers or young creative talent. To thrive in the digital economy and reverse declining performance trends, companies will have to fundamentally rethink their management approach by moving from knowledge stocks to knowledge flows, from scalable efficiency to scalable learning, from push organizations to pull organizations. Based on the outcomes of the Shift Index and on the book The Power of Pull, the first episode of the Social Business Thought-Leaders features John Hagel to provide strategic insights on how companies will succeed in the 21st century.

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  • Html5 Input Validation Presentation

    - by srkirkland
    Last week I gave a presentations to the 2011 UC Davis IT Security Symposium that covered input validation features in HTML5.  I mostly discussed the following three topics: New Html5 Input Types (like <input type=”email” />) Html5 Constraints (like <input type=”text” required maxlength=”8” />) Polyfills The slides only cover part of the story since there are a few “live demos.”  You can find all of the demo code on my github repository https://github.com/srkirkland/ITSecuritySymposium.  You’ll need ASP.NET Mvc 3 installed to run them. The slides are also available in my GitHub repository, but I’ve also added them to slideshare as well because that’s what the cool kids do: http://www.slideshare.net/srkirkland/data-validation-in-web-applications. I believe the presentation was well received and most people learned something, so I just wanted to share.  When loading up the Html5 demo just click on the Html5 tab and go through each example. Enjoy!   [Examples from the Slides and Demos]  

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  • C# 4.0: Alternative To Optional Arguments

    - by Paulo Morgado
    Like I mentioned in my last post, exposing publicly methods with optional arguments is a bad practice (that’s why C# has resisted to having it, until now). You might argument that your method or constructor has to many variants and having ten or more overloads is a maintenance nightmare, and you’re right. But the solution has been there for ages: have an arguments class. The arguments class pattern is used in the .NET Framework is used by several classes, like XmlReader and XmlWriter that use such pattern in their Create methods, since version 2.0: XmlReaderSettings settings = new XmlReaderSettings(); settings.ValidationType = ValidationType.Auto; XmlReader.Create("file.xml", settings); With this pattern, you don’t have to maintain a long list of overloads and any default values for properties of XmlReaderSettings (or XmlWriterSettings for XmlWriter.Create) can be changed or new properties added in future implementations that won’t break existing compiled code. You might now argue that it’s too much code to write, but, with object initializers added in C# 3.0, the same code can be written like this: XmlReader.Create("file.xml", new XmlReaderSettings { ValidationType = ValidationType.Auto }); Looks almost like named and optional arguments, doesn’t it? And, who knows, in a future version of C#, it might even look like this: XmlReader.Create("file.xml", new { ValidationType = ValidationType.Auto });

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  • How to implement curved movement while tracking the appropriate angle?

    - by Vexille
    I'm currently coding a 2D top-down car game which will be turn-based. And since it's turn-based, the cars won't be controlled directly (i.e. with a simple velocity vector that adjusts its angle when the player wants to turn), but instead it's movement path has to be planned beforehand, and then the car needs to follow the path when the turn ends (think Steambirds). This question has some interesting information, but its focus is on homing-missile behaviour, which I kinda had figured out, but doesn't really apply to my case, I think, since I need to show a preview of the path when the player is planning his turn, then have the car follow that path. In that same question, there's an excellent answer by Andrew Russel which mentions Equations of Motion and Bézier's Curve. Some of his other suggestions of implementation are specific to XNA though, so they don't help much (I'm using Marmalade SDK). If I assume Bézier's Curve as the solution of choice, I'm left with one specific problem: I'll have the car's position (the first endpoint) and the target/final position (the last endpoint), but what should I use as the control point (assuming a square/quadratic curve)? And whether I use Bézier's Curve or another parametric equation, I'd still be left with another issue: the car can't just follow the curve, it must turn (i.e. adjust its angle) accordingly. So how can I figure out which way the car should be pointing to at any given point in the curve?

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  • scalability with nginx, passenger, ruby on rails setup

    - by Dani Cela
    Hey guys I had a question regarding scalability for my RoR application. We have been optimizing our application over the last few days and after running blitz.io, notice that our application times out after maybe 1000 hits in 30 seconds we experienced massive timeouts. In the 1 minute test apparently 74% of users would have timed out. Look at the performance of my website: http://blitz.io/report/1c8eb2f395a5eadeabd62fd831ada9e5 Not saying that our website will in any way experience this now, but I wish to design the infrastructure to handle this. What is normally done in this situation? Currently we have one web server and one database server. Would load balancing be the route to go?

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  • C#/.NET Little Wonders: The EventHandler and EventHandler&lt;TEventArgs&gt; delegates

    - by James Michael Hare
    Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. In the last two weeks, we examined the Action family of delegates (and delegates in general), and the Func family of delegates and how they can be used to support generic, reusable algorithms and classes. So this week, we are going to look at a handy pair of delegates that can be used to eliminate the need for defining custom delegates when creating events: the EventHandler and EventHandler<TEventArgs> delegates. Events and delegates Before we begin, let’s quickly consider events in .NET.  According to the MSDN: An event in C# is a way for a class to provide notifications to clients of that class when some interesting thing happens to an object. So, basically, you can create an event in a type so that users of that type can subscribe to notifications of things of interest.  How is this different than some of the delegate programming that we talked about in the last two weeks?  Well, you can think of an event as a special access modifier on a delegate.  Some differences between the two are: Events are a special access case of delegates They behave much like delegates instances inside the type they are declared in, but outside of that type they can only be (un)subscribed to. Events can specify add/remove behavior explicitly If you want to do additional work when someone subscribes or unsubscribes to an event, you can specify the add and remove actions explicitly. Events have access modifiers, but these only specify the access level of those who can (un)subscribe A public event, for example, means anyone can (un)subscribe, but it does not mean that anyone can raise (invoke) the event directly.  Events can only be raised by the type that contains them In contrast, if a delegate is visible, it can be invoked outside of the object (not even in a sub-class!). Events tend to be for notifications only, and should be treated as optional Semantically speaking, events typically don’t perform work on the the class directly, but tend to just notify subscribers when something of note occurs. My basic rule-of-thumb is that if you are just wanting to notify any listeners (who may or may not care) that something has happened, use an event.  However, if you want the caller to provide some function to perform to direct the class about how it should perform work, make it a delegate. Declaring events using custom delegates To declare an event in a type, we simply use the event keyword and specify its delegate type.  For example, let’s say you wanted to create a new TimeOfDayTimer that triggers at a given time of the day (as opposed to on an interval).  We could write something like this: 1: public delegate void TimeOfDayHandler(object source, ElapsedEventArgs e); 2:  3: // A timer that will fire at time of day each day. 4: public class TimeOfDayTimer : IDisposable 5: { 6: // Event that is triggered at time of day. 7: public event TimeOfDayHandler Elapsed; 8:  9: // ... 10: } The first thing to note is that the event is a delegate type, which tells us what types of methods may subscribe to it.  The second thing to note is the signature of the event handler delegate, according to the MSDN: The standard signature of an event handler delegate defines a method that does not return a value, whose first parameter is of type Object and refers to the instance that raises the event, and whose second parameter is derived from type EventArgs and holds the event data. If the event does not generate event data, the second parameter is simply an instance of EventArgs. Otherwise, the second parameter is a custom type derived from EventArgs and supplies any fields or properties needed to hold the event data. So, in a nutshell, the event handler delegates should return void and take two parameters: An object reference to the object that raised the event. An EventArgs (or a subclass of EventArgs) reference to event specific information. Even if your event has no additional information to provide, you are still expected to provide an EventArgs instance.  In this case, feel free to pass the EventArgs.Empty singleton instead of creating new instances of EventArgs (to avoid generating unneeded memory garbage). The EventHandler delegate Because many events have no additional information to pass, and thus do not require custom EventArgs, the signature of the delegates for subscribing to these events is typically: 1: // always takes an object and an EventArgs reference 2: public delegate void EventHandler(object sender, EventArgs e) It would be insane to recreate this delegate for every class that had a basic event with no additional event data, so there already exists a delegate for you called EventHandler that has this very definition!  Feel free to use it to define any events which supply no additional event information: 1: public class Cache 2: { 3: // event that is raised whenever the cache performs a cleanup 4: public event EventHandler OnCleanup; 5:  6: // ... 7: } This will handle any event with the standard EventArgs (no additional information).  But what of events that do need to supply additional information?  Does that mean we’re out of luck for subclasses of EventArgs?  That’s where the generic for of EventHandler comes into play… The generic EventHandler<TEventArgs> delegate Starting with the introduction of generics in .NET 2.0, we have a generic delegate called EventHandler<TEventArgs>.  Its signature is as follows: 1: public delegate void EventHandler<TEventArgs>(object sender, TEventArgs e) 2: where TEventArgs : EventArgs This is similar to EventHandler except it has been made generic to support the more general case.  Thus, it will work for any delegate where the first argument is an object (the sender) and the second argument is a class derived from EventArgs (the event data). For example, let’s say we wanted to create a message receiver, and we wanted it to have a few events such as OnConnected that will tell us when a connection is established (probably with no additional information) and OnMessageReceived that will tell us when a new message arrives (probably with a string for the new message text). So for OnMessageReceived, our MessageReceivedEventArgs might look like this: 1: public sealed class MessageReceivedEventArgs : EventArgs 2: { 3: public string Message { get; set; } 4: } And since OnConnected needs no event argument type defined, our class might look something like this: 1: public class MessageReceiver 2: { 3: // event that is called when the receiver connects with sender 4: public event EventHandler OnConnected; 5:  6: // event that is called when a new message is received. 7: public event EventHandler<MessageReceivedEventArgs> OnMessageReceived; 8:  9: // ... 10: } Notice, nowhere did we have to define a delegate to fit our event definition, the EventHandler and generic EventHandler<TEventArgs> delegates fit almost anything we’d need to do with events. Sidebar: Thread-safety and raising an event When the time comes to raise an event, we should always check to make sure there are subscribers, and then only raise the event if anyone is subscribed.  This is important because if no one is subscribed to the event, then the instance will be null and we will get a NullReferenceException if we attempt to raise the event. 1: // This protects against NullReferenceException... or does it? 2: if (OnMessageReceived != null) 3: { 4: OnMessageReceived(this, new MessageReceivedEventArgs(aMessage)); 5: } The above code seems to handle the null reference if no one is subscribed, but there’s a problem if this is being used in multi-threaded environments.  For example, assume we have thread A which is about to raise the event, and it checks and clears the null check and is about to raise the event.  However, before it can do that thread B unsubscribes to the event, which sets the delegate to null.  Now, when thread A attempts to raise the event, this causes the NullReferenceException that we were hoping to avoid! To counter this, the simplest best-practice method is to copy the event (just a multicast delegate) to a temporary local variable just before we raise it.  Since we are inside the class where this event is being raised, we can copy it to a local variable like this, and it will protect us from multi-threading since multicast delegates are immutable and assignments are atomic: 1: // always make copy of the event multi-cast delegate before checking 2: // for null to avoid race-condition between the null-check and raising it. 3: var handler = OnMessageReceived; 4: 5: if (handler != null) 6: { 7: handler(this, new MessageReceivedEventArgs(aMessage)); 8: } The very slight trade-off is that it’s possible a class may get an event after it unsubscribes in a multi-threaded environment, but this is a small risk and classes should be prepared for this possibility anyway.  For a more detailed discussion on this, check out this excellent Eric Lippert blog post on Events and Races. Summary Generic delegates give us a lot of power to make generic algorithms and classes, and the EventHandler delegate family gives us the flexibility to create events easily, without needing to redefine delegates over and over.  Use them whenever you need to define events with or without specialized EventArgs.   Tweet Technorati Tags: .NET, C#, CSharp, Little Wonders, Generics, Delegates, EventHandler

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  • Core Audio sound driver has an error

    - by Raj More
    I have been using Virtual DJ on my machine. The setup is where I want audio to play over the headphones and use a USB sound card to play audio into my headphones so I can listen to music before I play it for everybody. However, the last time I tried, I got an error message saying "Error in the sound driver of Core Audio. Your sound card is probably not connected, or the settings are incorrect". If I use the headphone by themselves, the USB sound card by itself, or my speakers by themselves, they all work individually. How do I go about figuring out what's wrong here?

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