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  • C# Using singleton instead of a global static instance

    - by Farstucker
    I ran into a problem today and a friend recommended I use a global static instance or more elegantly a singleton pattern. I spent a few hours reading about singletons but a few things still escape me. Background: What Im trying to accomplish is creating an instance of an API and use this one instance in all my classes (as opposed to making a new connection, etc). There seems to be about 100 ways of creating a singleton but with some help from yoda I found some thread safe examples. ..so given the following code: public sealed class Singleton { public static Singleton Instance { get; private set; } static Singleton() { Instance = new Singleton(); } } How/Where would you instantiate the this new class and how should it be called from a separate class? Thanks for your help.

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  • How can I create a qr// in Perl 5.12 from C?

    - by kristina
    This has been working for me in 5.8 and 5.10, but in 5.12 my code creates this weird non-qr object: # running "print Dumper($regex)" $VAR1 = bless( do{\(my $o = '')}, 'Regexp' ); Whereas printing a qr// not created by my code looks like this: # running "print Dumper(qr/foo/i)" $VAR1 = qr/(?i-xsm:foo)/; My code is basically: REGEXP *rx = re_compile(pattern, flags); SV *regex = sv_2mortal(newSVpv("",0)); sv_magic(regex, (SV*)rx, PERL_MAGIC_qr, 0, 0); stash = gv_stashpv("Regexp", 0); sv_bless(newRV((SV*)regex), stash); Anyone know how to correctly create a regex from a string in 5.12?

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  • string parsing and substring in c

    - by Josh
    I'm trying to parse the string below in a good way so I can get the sub-string stringI-wantToGet: const char *str = "Hello \"FOO stringI-wantToGet BAR some other extra text"; str will vary in length but always same pattern - FOO and BAR What I had in mind was something like: const char *str = "Hello \"FOO stringI-wantToGet BAR some other extra text"; char *probe, *pointer; probe = str; while(probe != '\n'){ if(probe = strstr("\"FOO")!=NULL) probe++ else probe = ""; // Nulterm part if(pointer = strchr(probe, ' ')!=NULL) pointer = '\0'; // not sure here, I was planning to separate it with \0's } Any help will be appreciate it.

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  • Why implement DB connection pointer object as a reference counting pointer? (C++)

    - by DVK
    At our company one of the core C++ classes (Database connection pointer) is implemented as a reference counting pointer. To be clear, the objects are NOT DB connections themselves, but pointers to a DB connection object. The library is very old, and nobody who designed is around anymore. So far, nether I, nor any C++ experts in the company that I asked have come up with a good reason for why this particular design was chosen. Any ideas? It is introducing some problems (partially due to awful reference pointer implementation used), and I'm trying to understand if this design actually has some deep underlying reasons? The usage pattern these days seems to be that the DB connection pointer object is returned by a DB connection manager class, and it's somewhat unclear whether DB connection pointers were designed to be able to be used independently of DB connection manager.

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  • Can this be done with single SQL query

    - by Ghostrider
    I'm using MySQL. I have a table Type SubType 1 1 1 5 1 6 1 8 2 2 2 3 3 1 3 2 3 3 For each type there is some number of subtypes. For every subtype in a type there is a corresponding subtype in the next type: (1,1) => (2,2) (1,5) => (2,3) (1,6) => (2,2) (1,8) => (2,3) (2,2) => (3,1) (2,3) => (3,2) In case you haven't seen the pattern, here it is: you sort both current and next types by subtype, then in the next type you get subtype in the same position as your current subtype in current type is. If there are more subtypes in the current type that in the next one, you warp around and start from the first subtype in the next type. Is it possible to construct a query that takes current type and subtype and returns corresponding subtype in the next type?

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  • Customizing UISlider look

    - by tcurdt
    To customize the visual look of a UISlider you can set the thumb and track images. Part of the track images gets stretched to the appropriate with. From the documentation: A stretchable region sits between two end cap regions. The end caps define the portions of the image that remain as is and are not stretched. The stretchable region is a 1-point wide area between the end caps that can be replicated to make the image appear longer. Now the problem I have is that my stretchable region needs to be more than 1-point wide. (It's a pattern) Unfortunately the 1-point width seems to be hard coded in the SDK. Anyone having an idea how to work around this? Or will I have to write my own slider from scratch for this?

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  • how to fetch a range of files from an FTP server using C#

    - by user260076
    hello all, i'm stuck at a point where i am using a wildcard parameter with the FtpWebRequest object as suck FtpWebRequest reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + ftpServerIP + "/" + WildCard)); now this works fine, however i now want to fetch a specific range of files. say the file naming structure is *YYYYMMDD.* and i need to fetch all the files prior to today's date. i've been searching for a wildcard pattern for that with no good results, one that will work in a simple file listing. and it doesn't look like i can use regex here. any thoughts ?

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  • how to open many files simultaneously for reading in c

    - by monkeyking
    I'm trying to port some of my c++ code into c. I have the following construct class reader{ private: FILE *fp; alot_of_data data;//updated by read_until() method public: reader(const char*filename) read_until(some conditional dependent on the contents of the file, and the arg supplied) } Im then instantiating hundreds of these object and iterate over them using several 'read_until()' for each file until allfiles is at eof. I'm failing to see any clever way to do this in c, the only solution I can come up with is making an array of FILE pointers, and do the same with all the private member data from my class. But this seems very messy, can I implement the functionality of my class as a function pointer, or anything better, I think I'm missing a fundamental design pattern? The files are way to big to have all in memory, so reading everything from every file is not feasible Thanks

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  • Avoiding Nested Blocks

    - by Helium3
    If there is a view controller that wants to execute a number of block based tasks one at a time, how can the control be given back to the view controller after a completion block has executed. Lets say ViewControllerOne wants to execute a number of tasks, each relying on the result of the previous one, how would this control be given back to the viewcontroller after each completion block has been executed? I started thinking about this and I was heading towards a deeply nested block pattern that will surely only cause confusion to whoever else reads or tests it. A task executes and the completion block returns the result or error which is needed by the next task, which has its own completion task, that the next task relies on and so forth. How can the control be managed in one place, the viewcontroller? Would the completion block just call the next function that handles the next task, using a pointer to the view controller?

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  • Are there programming languages that rely on non-latin alphabets?

    - by Jaxsun
    Every programming language I have ever seen has been based on the Latin alphabet, this is not surprising considering I live in Canada... But it only really makes sense that there would be programming languages based on other alphabets, or else bright computer scientists across the world would have to learn a new alphabet to go on in the field. I know for a fact that people in countries dominated by other alphabets develop languages based off the Latin alphabet (eg. Ruby from Japan), but just how common is it for programming languages to be based off of other alphabets like Arabic, or Cyrillic, or even writing systems which are not alphabetic but rather logographic in nature such as Japanese Kanji? Also are any of these languages in active widespread use, or are they mainly used as teaching tools? This is something that has bugged me since I started programming, and I have never run across someone who could think of a real answer.

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  • Efficient storage/retrieval method for replayable comet style applications (Google Wave, Etherpad)

    - by Gareth Simpson
    I am considering a web application that would have the same kind of multi user, automatic saving, infinite undo / replay capabilities that you see in Google Wave and Etherpad (albeit on a drastically smaller scale and userbase). Before I go away and reinvent the wheel, is this something that has already been addressed as either a piece of technology or library, or even just a design pattern. I know this isn't necessarily the best Stack Overflow question as there is probably not a "right" answer, but my Google-fu has failed me and I'd just like a reading list! Ordinarily I would be developing under python/django but this is not a firm requirement just a preference :)

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  • Is it possible to listen to relational database update?

    - by Morgan Cheng
    Is it possible to listen to relation database update? For example, my web app want to send data update to client through Comet technology. I can have the program to poll the database periodically, but that would not be performant and scalable. If app can hood to a "event handler" of database, then app can get notification every time given database table data is updated. This sounds more promising, but I didn't find any concrete example for it. This is listener pattern. Does common relational database support such feature?

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  • Using polyfit to predict where the object falls ?

    - by ZaZu
    Hi there, I have information of an object being thrown at a parabolic pattern. There are 30 images in total taken at specific intervals from the start position till the end. Now I have managed to extract the x,y coordinates of the object being thrown in all 30 images... I think that using polyfit (or maybe polyval ? ) may help me predict where the object will fall after the first 15 images ... I just want to know, how can polyfit be used with the 30 x,y coordinates I have ? ( I have a loop to extract each image from a mat file 1 row at a time until 30 .. and then plot that image .. so should I use polyfit in the same loop before/after the plot ??? Any ideas ?? Thanks !

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  • How to append to an XML response an error attribute using Ruby on Rails 3?

    - by user502052
    I am trying to implement REST APIs, so in my RoR3 application I have XML responses. Before to pass to a consumer the XML, I wuold like to check if there are errors and, if so, send back a response with error messages. I read "Active Record Validations and Callbacks" guides on the RoR website, but it seems not work in my case. I extract from the database a resource doing @response = User.find_by_id(1) and I wuold like, if possible, to add error to it. Seeing some examples I have seen how to report errors in an XML file format.xml { render :xml => @response.errors } but how I can add append new errors to the @response? Maybe something like this: errors.add(:password, "is invalid")

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  • Swing Timer in Conjunction with Possible Long-running Background Task

    - by javacavaj
    I need to perform a task repeatedly that affects both GUI-related and non GUI-related objects. One caveat is that no action should performed if the previous task had not completed when the next timer event is fired. My initial thoughts are to use a SwingTimer in conjunction with a javax.swing.SwingWorker object. The general setup would look like this. class { timer = new Timer(speed, this); timer.start(); public void actionPerformed(ActionEvent e) { SwingWorker worker = new SwingWorker() { @Override public ImageIcon[] doInBackground() { // potential long running task } @Override public void done() { // update GUI on event dispatch thread when complete } } } Some potential issues I see with this approach are: 1) Multiple SwingWorkers will be active if a worker has not completed before the next ActionEvent is fired by the timer. 2) A SwingWorker is only designed to be executed once, so holding a reference to the worker and reusing (is not?) a viable option. Is there a better way to achieve this?

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  • Rails find_or_create by more than one attribute?

    - by tybro0103
    There is a handy dynamic attribute in active-record called find_or_create_by: Model.find_or_create_by_<attribute>(:<attribute> => "") But what if I need to find_or_create by more than one attribute? Say I have a model to handle a M:M relationship between Group and Member called GroupMember. I could have many instances where member_id = 4, but I don't ever want more than once instance where member_id = 4 and group_id = 7. I'm trying to figure out if it's possible to do something like this: GroupMember.find_or_create(:member_id => 4, :group_id => 7) I realize there may be better ways to handle this, but I like the convenience of the idea of find_or_create.

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  • C# Processing Enter Key on Custom Container

    - by tycobb
    I am currently building a custom container control. Everything was going along smoothly until I hit a snag during testing. I noticed that the Enter key is not getting processed to the control that has focus inside the container. Everything else works as expected though. I am able to click the button with either the mouse or space bar, but enter does not want to get processed. After doing endless searches on container controls and processing the enter key I have come up with no solution. I tried returning Enter as true in IsInputKey(Keys keyData) and that didn't work. Neither did setting KeyPreview on the form. I have tried it with my custom button and .NET's standard button. Like I mentioned earlier, spacebar will trigger the desired effect. Please tell me what I am missing. There has to be an easy / stupid simple way to get Enter to process over to the active child control.

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  • @@TRANCOUNT and a current connection

    - by AspOnMyNet
    Assume I connect to SQL server 2008 via SQL Server Management Studio ( SSMS ) and open new window W1 by clicking on New Query tab and write the following inside W1: BEGIN TRANSACTION; If I execute this statement 5 times, and then write (inside W1) SELECT @@TRANCOUNT; , then the value returned will be 5. But if I open another window W2 ( inside the same SSMS instance and thus on the same connection ) and write inside W2 SELECT @@TRANCOUNT; then value returned will be 0. @@TRANCOUNT variable returns the number of active transactions for the current connection. Both W1 and W2 windows were opened on the same connection, so shouldn’t ( according to the above quote ) in both W1 and W2 variable @@TRANCOUNT hold the same value? thanx

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  • htaccess Redirect - First Segment to PHP File, Second Segment as Parameter

    - by Steve
    My htaccess redirect knowledge is somewhat weak, so I was hoping to get some help here. I currently have the following redirect, which works well: # remove trailing slash RewriteRule ^(.*)/$ /$1 [L,R=301] # redirect to clean URL RewriteCond /%{REQUEST_FILENAME}.php -f RewriteRule ^([a-zA-Z0-9_-\s]+)$ /$1.php This takes a URL like www.mysite.com/about to www.mysite.com/about.php Now I would like to keep this behavior, but add parameters (if applicable), as such: www.mysite.com/about = www.mysite.com/about.php www.mysite.com/gallery/1 = www.mysite.com/gallery.php?id=1 If possible, I might like to expand this system to 2 or more parameters, as such: www.mysite.com/gallery/1/2 = www.mysite.com/gallery.php?id=1&section=2 So the pattern would be: First URL segment redirects to a PHP file (Optionally) the second segment gets added as the id parameter (Optionally) the third segment gets added as the section parameter

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  • Are today's young programmers getting wrapped around the axle with patterns and practices?

    - by Robert Harvey
    Recently I have noticed a number of questions on SO that look something like this: I am writing a small program to keep a list of the songs that I keep on my ipod. I'm thinking about writing it as a 3-tier MVC Ruby on Rails web application with TDD, DDD and IOC, using a factory pattern to create the classes and a singleton to store my application settings. Do you think I'm taking the right approach? Do you think that we're handing novice programmers a very sharp knife and telling them, "Don't cut yourself with this"? NOTE: Despite the humorous tone, this is a serious (and programming-related) question.

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  • Cheap windows driver signing for 64 bit Windows 7

    - by kayahr
    I need to install the libusb-win32 driver on Windows 7 64 bit machines. This driver is open source so it is not digitally signed so I want to do this my self but I wonder if this can be done WITHOUT paying lot of money. Is it possible to use a certificate which is NOT signed by Verisign or GlobalSign? Maybe self-signed or by using StartSSL instead? And if yes, how do I do it? According to this howto I have to use a "cross-certificate" (And there are only six available on the Microsoft list and most of them are for CAs which are no longer active) I don't care if the user is confronted with a warning message. I can even accept if the user has to install a special CA certificate first. I only require that the driver runs without manually disabling the signature check on each windows startup.

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  • Delegate won't update page

    - by mat690
    I am trying to change the active index of a multiview by using a delegate and it doesn't work as i expect. this is my code protected void ucWaitPage_FinishedWaiting(PerformAfterWaitDelegate performAfterWait) { performAfterWait.Invoke(); this.SetIndex(); } private void SetIndex() { this.mvwTest.ActiveViewIndex = 0; } The performAfterWait Delegate points to the SetIndex() method. When the performAfterWait delegate gets invoked SetIndex() gets called but when SetIndex() returns this.mvwTest.ActiveViewIndex reverts to being equal to 1. However when i call the SetIndex() method directly it sets this.mvwTest.ActiveViewIndex = 0 and the change persists when the method returns.

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  • How to use a 3rd party control inside the viewmodel?

    - by Sander
    I have a 3rd party control which among other things performs loading of some data. I want my viewmodel to keep track of this load operation and adjust its own state accordingly. If it were up to me, I'd do the data loading far away from the view, but it is not. So, I seem to be in the situation where my viewmodel depends on my view. How do I best handle this? I feel rather dirty making the view publish events to the viewmodel but I don't see any other reasonable way to get this info into the viewmodel. A similar situation might crop up with standard controls, too - imagine if your viewmodel depends on the events coming from a MediaElement - how do you properly model this? Do you put the MediaElement into the viewmodel? That doesn't sound right. If publishing the events to the viewmodel is indeed the most reasonable way, is there some common pattern used for this? How do you do it?

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  • Display Computer Info on an ASP.NET Page

    - by Gene
    I want to build a page for end users to visit (in our MPLS Network) and it show the following information in regards to them: Computer Name OS Disk Space Memory IP Address Active Directory User Name Password Expiration Time (As defined by Global Policy) Maybe a few other things such as Trend Micro Office current version vs. their version, # of MS Updates needed (we utilize WSUS), and a few other things in the future. My question is how would I pull this information from the user when they visit the page? What is the proper function for this? Anyone have examples they wish to share for me to learn by if possible?

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  • How to change Zend_Db_Table name within a Model to insert in multiple tables

    - by jwhat
    Using Zend Framework, I've created a Model to insert a record into a database. My question is, after $this->insert($data) how can I switch the active table so that I can insert a record into another table? Here's my code so far: class Model_DbTable_Foo extends Zend_Db_Table_Abstract { protected $_name = 'foo'; public function addFoo($params) { $data = array( 'foo' => $params['foo'], ); $this->insert($data); $foo_id = $this->getAdapter()->lastInsertId(); $data2 = array( 'bar' => $params['bar'] ); // I need to change the Db Table name here. $this->insert($data2); $bar_id = $this->getAdapter()->lastInsertId(); } }

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