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Articles indexed in August 2014

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• Already 3,333 tweets...

  Almost everything is about numbers, and this short blog entry includes the number of tweets written so far. ;) Quite frankly, I joined the Twitter bandwagon late... February 2010 or so. And within those 4.5 years I just came across an interesting milestone: 3,333 tweets 3,333 tweets since February 2010 Compared to some of my fellows here from Mauritius that's almost nothing... Anyways, Cheers and for the next 3,333 tweets. This time faster, hopefully.

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• Prepared statement alternatives for this middle-man program?

  - by user2813274

  I have an program that is using a prepared statement to connect and write to a database working nicely, and now need to create a middle-man program to insert between this program and the database. This middle-man program will actually write to multiple databases and handle any errors and connection issues. I would like advice as to how to replicate the prepared statements such as to create minimal impact to the existing program, however I am not sure where to start. I have thought about creating a "SQL statement class" that mimics the prepared statement, only that seems silly. The existing program is in Java, although it's going to be networked anyways so I would be open to writing it in just about anything that would make sense. The databases are currently MySQL, although I would like to be open to changing the database type in the future. My main question is what should the interface for this program look like, and does doing this even make sense? A distributed DB would be the ideal solution, but they seem overly complex and expensive for my needs. I am hoping to replicate the main functionality of a distributed DB via this middle-man. I am not too familiar with sql-based servers distributing data (or database in general...) - perhaps I am fighting an uphill battle by trying to solve it via programming, but I would like to make an attempt at least.

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• API always returns JSONObject or JSONArray Best practices

  - by Michael Laffargue

  I'm making an API that will return data in JSON. I also wanted on client side to make an utility class to call this API. Something like : JSONObject sendGetRequest(Url url); JSONObject sendPostRequest(Url url, HashMap postData); However sometimes the API send back array of object [{id:1},{id:2}] I now got two choices (): Make the method test for JSONArray or JSONObject and send back an Object that I will have to cast in the caller Make a method that returns JSONObject and one for JSONArray (like sendGetRequestAndReturnAsJSONArray) Make the server always send Arrays even for one element Make the server always send Objects wrapping my Array I going for the two last methods since I think it would be a good thing to force the API to send consistent type of data. But what would be the best practice (if one exist). Always send arrays? or always send objects?

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• Why does Linq to Entity Sum return null when the list is empty?

  - by Hannele

  There are quite a few questions on Stack Overflow about the Linq to Entity / Linq to SQL Sum extension method, about how it returns null when the result set is empty: 1, 2, 3, 4, 5, 6, 7, and many more, as well as a blog post discussing the issue here. Now, I could go a flag these as duplicates, but I feel it is still an inconsistency in the Linq implementation. I am assuming at this point that it is not a bug, but is more or less working as designed. I understand that there are workarounds (for example, casting the field to a nullable type, so you can coalesce with ??), and I also understand that for the underlying SQL, a NULL result is expected for an empty list. But because the result of the Sum extension for nullable types is also not nullable, why would the Linq to SQL / Linq to Entity Sum have been designed to behave this way?

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• decouple software components via nameconvention

  - by csteinmueller

  I'm currently evaluating alternatives to refactor a drivermanagement. In my multitier architecture I have Baseclass DAL.Device //my entity Interfaces BL.IDriver //handles the dataprocessing between application and device BL.IDriverCreator //creates an IDriver from a Device BL.IDriverFactory //handles the driver creation requests Every specialization of Device has a corresponding IDriver implementation and a corresponding IDriverCreator implementation. At the moment the mapping is fix via a type check within the business layer / DriverFactory. That means every new driver needs a) changing code within the DriverFactory and b) referencing the new IDriver implementation / assembly. On a customers point of view that means, every new driver, used or not, needs a complex revalidation of their hardware environment, because it's a critical process. My first inspiration was to use a caliburn micro like nameconvention see Caliburn.Micro: Xaml Made Easy BL.RestDriver BL.RestDriverCreator DAL.RestDevice After receiving the RestDevicewithin the IDriverFactory I can load all driver dlls via reflection and do a namesplitting/comparing (extracting the xx from xxDriverCreator and xxDevice) Another idea would be a custom attribute (which also leads to comparing strings). My question: is that a good approach above layer borders? If not, what would be a good approach?

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• How to manage security of these self hosted web apis, to ensure that the request coming for accessing data is authenticated?

  - by Husrat Mehmood

  Let's pretend I am going to work on an enterprise application. Say I have 11 modules in the application and I would have to develop Dashboards for every role in the organization for whom I are going to develop application. We Decided to use Asp.Net Web Api and return json data from our apis. We are going to include 11 Self hosted web apis projects in our application (one self hosted web api) for every module. All 11 modules are connected to one Sql server 2012 Database. Then once api is ready we would have to create Business Dashboards (Based upon roles in Organization). So Now my web api client is Asp.Net Mvc application.Asp.Net mvc will consume those web apis. Here is the part for whom all explanation is done. How should I manage Security of all 11 self hosted web apis? How should I only authenticated request is coming? If I authenticate user by login and password and then redirect user to appropriate Dashboard designed for the role that user have and load data by consuming web apis. How should I ensure that the request coming for accessing data is authenticated?

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• Is this JS code a good way for defining class with private methods?

  - by tigrou

  I was recently browsing a open source JavaScript project. The project is a straight port from another project in C language. It mostly use static methods, packed together in classes. Most classes are implemented using this pattern : Foo = (function () { var privateField = "bar"; var publicField = "bar";     function publicMethod() { console.log('this is public');     } function privateMethod() { console.log('this is private'); } return {   publicMethod : publicMethod, publicField : publicField }; })(); This was the first time I saw private methods implemented that way. I perfectly understand how it works, using a anonymous method. Here is my question : is this pattern a good practice ? What are the actual limitations or caveats ? Usually i declare my JavaScript classes like that : Foo = new function () { var privateField = "test"; this.publicField = "test";     this.publicMethod = function()     { console.log('this method is public'); privateMethod();     } function privateMethod() { console.log('this method is private'); } }; Other than syntax, is there any difference with the pattern show above ?

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• In a specification, should I describe what a product does (ideally) or what it should/must do?

  - by Arlaud Pierre

  I'm writting a German specification (I'm not German). Differences may appear for this process in different cultures, especially in the terminology, but usually here's the idea: The client writes his needs and wishes in a document, called a scope statement or requirements document. The supplier tries to understand the actual need of the client (which might be different to what was written and to what the client meant to say and to what the client thinks he needs, etc.) The supplier writes a specification for the product, which should fill the client's need. The specification needs to be precise enough for the product to be made (ambiguity problems occur). The client and the supplier can check whether they have understood each other, and discuss details of the product. The client agrees with the specification (or at least its current iteration) and the supplier is ready to start the work. (it may of course be expected of you to disagree with this process, but this is irrelevant to my problem): I'm now somewhere around the last two steps and I've been criticized because I wrote what the product must do, and not what it will do ideally. Usually along the lines of The product must be able to perform task A And I was expected to write The product performs task A This is a simple word play, but I feel saying what the product does, while the product isn't even on the way to be made yet, is wrong. I would tend to consider a specification as a contract of what the product is expected to do (what it must do and how it should do it), and not what it does. Said differently, I feel this is the specification and not the manual of the end product…… Should I say what the product must do or what it does?

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• Can anyone explain segmented sieve of eratosthenes [on hold]

  - by Utkarsh

  I've searched all over the web on implementation of segmented sieve of eratosthenes. But I found none of them suitable for a beginner. Can anyone explain me the underlying principle behind this method? EDIT: I know that in Sieve of Eratosthenes, we find all primes upto the square root of given number and cross out all multiples of them till the given number. But what do we exactly do in its segmented version?

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• Cross-platform & 3D mobile game development [on hold]

  - by Sylvia MBemba

  I am not a developer or programmer and, I am planning an educative project that will involve having students to develop a cross-platform, 3D mobile game, similar to the SimCity concept. I need to write a project requirement and I'd like to pick someone's brain to understand what's involved in developing such a project: Is it realistic to have one or two students to do it? and along their other modules at uni? How much time can it take to develop from scratch? what are the different skills required?

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• Finding a way to simplify complex queries on legacy application

  - by glenatron

  I am working with an existing application built on Rails 3.1/MySql with much of the work taking place in a JavaScript interface, although the actual platforms are not tremendously relevant here, except in that they give context. The application is powerful, handles a reasonable amount of data and works well. As the number of customers using it and the complexity of the projects they create increases, however, we are starting to run into a few performance problems. As far as I can tell, the source of these problems is that the data represents a tree and it is very hard for ActiveRecord to deterministically know what data it should be retrieving. My model has many relationships like this: Project has_many Nodes has_many GlobalConditions Node has_one Parent has_many Nodes has_many WeightingFactors through NodeFactors has_many Tags through NodeTags GlobalCondition has_many Nodes ( referenced by Id, rather than replicating tree ) WeightingFactor has_many Nodes through NodeFactors Tag has_many Nodes through NodeTags The whole system has something in the region of thirty types which optionally hang off one or many nodes in the tree. My question is: What can I do to retrieve and construct this data faster? Having worked a lot with .Net, if I was in a similar situation there, I would look at building up a Stored Procedure to pull everything out of the database in one go but I would prefer to keep my logic in the application and from what I can tell it would be hard to take the queried data and build ActiveRecord objects from it without losing their integrity, which would cause more problems than it solves. It has also occurred to me that I could bunch the data up and send some of it across asynchronously, which would not improve performance but would improve the user perception of performance. However if sections of the data appeared after page load that could also be quite confusing. I am wondering whether it would be a useful strategy to make everything aware of it's parent project, so that one could pull all the records for that project and then build up the relationships later, but given the ubiquity of complex trees in day to day programming life I wouldn't be surprised if there were some better design patterns or standard approaches to this type of situation that I am not well versed in.

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• Dependency injection in constructor, method or just use a static class instead?

  - by gaetanm

  What is the best between: $dispatcher = new Dispatcher($request); $dispatcher->dispatch(); and $dispatcher = new Dispatcher(); $dispatcher->dispatch($request); or even Dispatcher::dispatch($request); Knowing that only one method of this class uses the $request instance. I naturally tend to the last solution because the class have no other states, but by I feel that it may not be the best OOP solution.

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• What to Return with Async CRUD methods

  - by RualStorge

  While there is a similar question focused on Java, I've been in debates with utilizing Task objects. What's the best way to handle returns on CRUD methods (and similar)? Common returns we've seen over the years are: Void (no return unless there is an exception) Boolean (True on Success, False on Failure, exception on unhandled failure) Int or GUID (Return the newly created objects Id, 0 or null on failure, exception on unhandled failure) The updated Object (exception on failure) Result Object (Object that houses the manipulated object's ID, Boolean or status field to with success or failure indicated, Exception information if there was one, etc) The concern comes into play as we've started moving over to utilizing C# 5's Async functionality, and this brought the question up of how we should handle CRUD returns large-scale. In our systems we have a little of everything in regards to what we return, we want to make these returns standardized... Now the question is what is the recommended standard? Is there even a recommended standard yet? (I realize we need to decide our standard, but typically we do so by looking at best practices, see if it makes sense for us and go from there, but here we're not finding much to work with)

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• How to layer if statements when order of logic is irrelevant?

  - by jimmyjimmy

  Basically I have a series of logic in my website that can lead to 5 total outcomes. Basically two different if tests and then a catch all else statement. For example: if cond1: if mod1: #do things elif mod2: #do things elif cond2: if mod1: #do things elif mod2 #do things else: #do things I was thinking about rewriting it like this: if cond1 and mod1: #do things elif cond1 and mod2: #do things elif cond2 and mod1: #do things elif cond2 and mod2: #do things else: #do things Is there any real difference in these two coding options/a better choice for this kind of logic testing?

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• Develop in trunk and then branch off, or in release branch and then merge back?

  - by Torben Gundtofte-Bruun

  Say that we've decided on following a "release-based" branching strategy, so we'll have a branch for each release, and we can add maintenance updates as sub-branches from those. Does it matter whether we: develop and stabilize a new release in the trunk and then "save" that state in a new release branch; or first create that release branch and only merge into the trunk when the branch is stable? I find the former to be easier to deal with (less merging necessary), especially when we don't develop on multiple upcoming releases at the same time. Under normal circumstances we would all be working on the trunk, and only work on released branches if there are bugs to fix. What is the trunk actually used for in the latter approach? It seems to be almost obsolete, because I could create a future release branch based on the most recent released branch rather than from the trunk. Details based on comment below: Our product consists of a base platform and a number of modules on top; each is developed and even distributed separately from each other. Most team members work on several of these areas, so there's partial overlap between people. We generally work only on 1 future release and not at all on existing releases. One or two might work on a bugfix for an existing release for short periods of time. Our work isn't compiled and it's a mix of Unix shell scripts, XML configuration files, SQL packages, and more -- so there's no way to have push-button builds that can be tested. That's done manually, which is a bit laborious. A release cycle is typically half a year or more for the base platform; often 1 month for the modules.

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• Correct way to inject dependencies in Business logic service?

  - by Sri Harsha Velicheti

  Currently the structure of my application is as below Web App -- WCF Service (just a facade) -- Business Logic Services -- Repository - Entity Framework Datacontext Now each of my Business logic service is dependent on more than 5 repositories ( I have interfaces defined for all the repos) and I am doing a Constructor injection right now(poor mans DI instead of using a proper IOC as it was determined that it would be a overkill for our project). Repositories have references to EF datacontexts. Now some of the methods in the Business logic service require only one of the 5 repositories, so If I need to call that method I would end up instantiating a Service which will instatiate all 5 repositories which is a waste. An example: public class SomeService : ISomeService { public(IFirstRepository repo1, ISecondRepository repo2, IThirdRepository repo3) {} // My DoSomething method depends only on repo1 and doesn't use repo2 and repo3 public DoSomething() { //uses repo1 to do some stuff, doesn't use repo2 and repo3 } public DoSomething2() { //uses repo2 and repo3 to do something, doesn't require repo1 } public DoSomething3() { //uses repo3 to do something, doesn't require repo1 and repo2 } } Now if my I have to use DoSomething method on SomeService I end up creating both IFirstRepository,ISecondRepository and IThirdRepository but using only IFirstRepository, now this is bugging me, I can seem to accept that I am un-necessarily creating repositories and not using them. Is this a correct design? Are there any better alternatives? Should I be looking at Lazy instantiation Lazy<T> ?

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• Best approach for tracking dependent state

  - by Pace

  Let's pretend I work on a project tracking application. The application is a database backed, server hosted, web application. In this application there are Projects which have many Activities which have many Tasks. A Task has two date fields an originalDueDate and a projectedDueDate. In addition, there are dynamic fields on the Activities and the Projects which indicate whether the Activity or Project is behind schedule based on the projected due dates of the child tasks and various other variables such as remaining buffer time, etc. There are a number of things that can cause the projectedDueDate to change. For example, an employee working on the project may (via a server request) enter in a shipping delay. Alternatively, a site may (via a server request) enter in an unexpected closure. When any of these things occur I need to not only update the projectedDueDate of the Task but also trigger the corresponding Project and Activity to update as well. What is the best way to do this? I've thought of the observer pattern but I don't keep a single copy of all these objects in memory. When a request comes in, I query the Task in from the database, at that point there is no associated Activity in memory that would be a listener. I could remove the ability to query for Tasks and force the application to query first by Project, then by Activity (in context of Project), then by task (in context of Activity) adding the observer relationships at each step but I'm not sure if that is the best way. I could setup a database event listening system so when a Task modified event is dispatched I have a handler which queries for the Activity at that point. I could simply setup a two-way relationship between Task and Activity so that the Task knows about the parent Activity and when the Task updates his state the Task grabs his parent and updates state. Right now I'm stuck considering all the options and am wondering if any single approach (doesn't have to be a listed approach) is jumping out at others as the best approach.

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• Why doesn't libxml2 support XPath 2.0?

  - by Peter Krauss

  Libxml2 is the faster, stable and most popular "open DOM engine"... And the "XML C parser and toolkit of Gnome". The initial release of Libxml2 was September 1999, 13 years ago. XPath v1.0 was also released at 1999. XPath v2.0 became a recommendation on January 2007, 6 years ago. We can suppose that the Libxml2 community have time and people to develop a XPath2... So, what is the problem? Why doesn't libxml2 (or a "libxml2 fork" or an "experimental lib"!) support XPath 2.0? Some raised hypotheses to discussion at answers, Because Libxml2 community (and Gnome community) dislikes and have no motivation to develop something to XPath2 or xQuery. 1.1. XPath2 needs (by mathematical proof) a very heavy parser, much slower, etc. that is not suitable to real-world Libxml2 applications. 1.2. Other "ideologic" dislikes/motivations. Because it is written with C, and for XPath2 is better to develop with C++. Because the above hypothesis of "Libxml2 community have time and people" is false. Because XPath2 became stable in 2010 with its "Second Edition" release, and ~2.5 years is not (?) enough time.

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• Which parallel pattern to use?

  - by Wim Van Houts

  I need to write a server application that fetches mails from different mail servers/mailboxes and then needs to process/analyze these mails. Traditionally, I would do this multi-threaded, launching a thread for fetching mails (or maybe one per mailbox) and then process the mails. We are moving more and more to servers where we have 8+ cores, so I would like to make use of these cores as much as possible (and not use 1 at 100% and leave the seven others untouched). So conceptually, as an example, it would be nice that I could write the application in such a way that two cores are "continuously" fetching emails and four cores are "continuously" processing/analyzing the emails (since processing and analyzing mails is more CPU intensive than fetching mails). This seems like a good concept, but after studying some parallel patterns, I'm not really sure how this is best implemented. None of the patterns really fit. I'm working in VS2012, native C++, but I guess from a design point of view this does not really matter and just some pointers on how to organize this would be great!

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• What are the pros and cons of Coffeescript?

  - by Philip

  Of course one big pro is the amount of syntactic sugar leading to shorter code in a lot of cases. On http://jashkenas.github.com/coffee-script/ there are impressive examples. On the other hand I have doubts that these examples represent code of complex real world applications. In my code for instance I never add functions to bare objects but rather to their prototypes. Moreover the prototype feature is hidden from the user, suggesting classical OOP rather than idiomatic Javascript. The array comprehension example would look in my code probably like this: cubes = $.map(list, math.cube); // which is 8 characters less using jQuery...

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• Ubuntu 12.04 PXELINUX does not boot RHEL Kernel and Initrd

  - by utpal

  I have successfully setup PXE server on Ubuntu 12.04 with DNSMASQ for DHCP Proxy Service, TFTPD-HPA for TFTP service, NFS-KERNEL-SERVER, APACHE2 and SYSLINUX for pxelinux.0 bootloaded needed for pxe boot using the following POST: http://ubuntuforums.org/showthread.php?t=1606910 I was successfully able to pxe boot a client to a Ubuntu 12.04 LIVE CD. Next, I want to PXE boot a client to a RHEL 6.5 x64 Kernel and initrd image. I dont want to install, just boot a client so that it mounts initrd and I can get a minimal filesystem on the client. How can I do that? Please Help!!

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• Using "MTNL 3G Jadoo" data card on Ubuntu

  - by amolbk

  I am trying to use "MTNL 3G Jadoo" data card (Teracom LW272) with Ubuntu 12.04. On connecting, it gets mounted as a drive containing the client installation .deb file. I opened the .deb file in Ubuntu Software Center and installed it. I searched for "MTNL" in Ubuntu search and found "MTNL 3G Modem" application. But it won't run. I found it is installed in /opt/MTNL-3GModem. I tried running it from the terminal as: sudo /opt/MTNL-3GModem/ModemClient, but no luck. Any idea how to get it working?

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• How can I run Tellme more software on Ubuntu 14.04 LTS?

  - by Alex Walker

  I'm new to Ubuntu and I've been loving it so far, I have it on my 2 computers and I think everyone should try it. I run an English Laboratory in a University (Our PC's are old and slow) so I want to install Ubuntu on all of them so the students can have a better experience here, the problem is tha we NEED Tell me more Software which I believe it's only for windiws. How can I install it in ubuntu? do I need wine or a virtual machine with Windows? please help! and thank you so much!!

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• Why is my LAN not working properly ?

  - by ps06756

  I am using Ubuntu 12.04 as my OS. Till yesterday, my LAN was working fine , but after that my LAN is not working properly. What I mean is that it shows that the LAN wire is connected properly, but when I try to open a website it gets stuck on resolving host. I am using the web browser as Google-chrome. Now, when I manually switch off the wired connection and turn it on again, the LAN works perfectly till I open one or two webpages. After that the same problem repeats again. Can anybody, help me with a solution to this problem.

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• Why doesn't lsof show localhost TCP connections in 14.04?

  - by sfussenegger

  I have two servers running 12.04.4 and 14.04.1 respectively. Both have nginx (port 80) and a Java process (port 8080). As expected, the lsof output for the Java process on the 12.04 machine shows a couple of established connections for port 8080 (e.g. TCP 127.0.0.1:8080->127.0.0.1:58067 (ESTABLISHED)) The 14.04 machine however does not. It only shows the listening port (TCP *:8080 (LISTEN)). I'm sure there are active connections though (confirmed by access logs, Java process status output, etc). What has changed from 12.04 to result in this behavior? Can this change be the cause for the "Too many open files" errors I'm getting since moving from 12.04 to 14.04? 12.04: $ dpkg -l lsof linux-image-virtual openjdk-7-jre nginx ||/ Name Version +++-===========================================-=========================================== ii linux-image-virtual 3.2.0.59.70 ii lsof 4.81.dfsg.1-1build1 ii nginx 1.6.1-1~precise ii openjdk-7-jre 7u65-2.5.1-4ubuntu1~0.12.04.1 14.04: $ dpkg -l lsof linux-image-virtual openjdk-7-jre nginx-full ||/ Name Version Architecture Description +++-=====================================-=======================-======================= ii linux-image-virtual 3.13.0.32.38 amd64 ii lsof 4.86+dfsg-1ubuntu2 amd64 ii nginx-full 1.4.6-1ubuntu3 amd64 ii openjdk-7-jre:amd64 7u65-2.5.1-4ubuntu1~0.1 amd64

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