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• Windows service hangs

  - by Ram

  Hi, I have a webdav client-server application. I'm using Cassini webserver to host the webdav server. One important thing here is that I start and Stop my webserver using a windows service. Now, I start my windows service and I attach my webdav server application's debugger to the windows service. Everything used to go fine, that is I could connect to the server using my webdav client, debug the server code. However, a couple of days back, when I tried to debug my webdav server application, which in turn is attached to a windows service, my computer freezes while I'm in the midst of debugging the server app. The freeze does not occur at the same line every time and is therefore not predictable. Every time this happens, I would not be able to do anything at all with my computer except to reboot the system using the power button. What could be the problem? Could it be the service that is freezing or something else? Any help? Thanks, Ram

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• What's the best way to learn .NET?

  - by duffymo

  I've been developing Java EE for quite a while now. I've used WebLogic, Tomcat, Spring, and Hibernate extensively, so I have a mental model of what features are available and how things are developed and deployed. The problem that I have with .NET is that I don't have a clear mapping of its features onto Java EE. Here's what I know so far: Java EE - .NET Java - C# JAR - DLL WAR - ? (deployment in general) EAR - ? (deployment in general) Tomcat - IIS web server JSP - ASP? JDBC - ODBC JMS - MSMQ JTA - Microsoft Transaction Manager So much of the functionality that WebLogic handles appears to be dispersed throughout the Windows OS. My confusion kicks in when I see the waves of books at Borders - VB.NET, ASP.NET, C#, etc. If I'm not a VB programmer, would it be possible to stick with C# and write enterprise apps that are the equivalent of what I'm used to with Java EE? If there were a Top Three list of books to learn from, what would they be? The "Head First" series has certainly been successful for Java. http://www.amazon.com/Head-First-C-Brain-Friendly-Guides/dp/0596514824/ref=sr_1_1?ie=UTF8&s=books&qid=1224121193&sr=8-1 Equally well recommended for .NET learning? Thanks. - %

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• Generating easy-to-remember random identifiers

  - by Carl Seleborg

  Hi all, As all developers do, we constantly deal with some kind of identifiers as part of our daily work. Most of the time, it's about bugs or support tickets. Our software, upon detecting a bug, creates a package that has a name formatted from a timestamp and a version number, which is a cheap way of creating reasonably unique identifiers to avoid mixing packages up. Example: "Bug Report 20101214 174856 6.4b2". My brain just isn't that good at remembering numbers. What I would love to have is a simple way of generating alpha-numeric identifiers that are easy to remember. Examples would be "azil3", "ulmops", "fel2way", etc. I just made these up, but they are much easier to recognize when you see many of them at once. I know of algorithms that perform trigram analysis on text (say you feed them a whole book in German) and that can generate strings that look and feel like German words. This requires lots of data, though, and makes it slightly less suitable for embedding in an application just for this purpose. Do you know of anything else? Thanks! Carl

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• Streamlining my javascript with a function

  - by liz

  i have a series of select lists, that i am using to populate text boxes with ids. so you click a select option and another text box is filled with its id. with just one select/id pair this works fine, but i have multiples, and the only thing that changes is the id of the select and input.. in fact just the ending changes, the inputs all start with featredproductid and the select ids all start with recipesproduct and then both end with the category. i know that listing this over and over for each category is not the way to do it. i think i need to make an array of the categories var cats = ['olive oil', "grains", "pasta"] and then use a forEach function? maybe? here is the clunky code window.addEvent('domready', function() { $('recipesproductoliveoil').addEvent('change', function(e){ pidselected = this.options[this.selectedIndex].getProperty('value') ; $("featuredproductidoliveoil").setProperties({ value: pidselected}); ; }); $('recipesproductgrains').addEvent('change', function(e){ pidselected = this.options[this.selectedIndex].getProperty('value') ; $("featuredproductidgrains").setProperties({ value: pidselected}); ; }); $('recipesproductpasta').addEvent('change', function(e){ pidselected = this.options[this.selectedIndex].getProperty('value') ; $("featuredproductidpasta").setProperties({ value: pidselected}); ; }); $('recipesproductpantry').addEvent('change', function(e){ pidselected = this.options[this.selectedIndex].getProperty('value') ; $("featuredproductidpantry").setProperties({ value: pidselected}); ; }); }); keep in mind this is mootools 1.1 (no i cant update it sorry). i am sure this is kind of basic, something i seem to have wrapping my brain around. but i am quite sure doing it as above is not really good...

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• Selecting a whole database over an individual table to output to file

  - by Daniel Wrigley

  :::::::: EDIT :::::::: New code for people to have a look at, one question I have with this is where do I set were the *.gz file is saved? $backupFile = $dbname . date("Y-m-d-H-i-s") . '.gz'; $command = "mysqldump --opt -h $dbhost -u $dbuser -p $dbpass $dbname | gzip > $backupFile"; system($command); Also why the hell can you not reply yo your own post with answering it? :( :::::::: EDIT :::::::: Ok Im having trouble finding out how to select a full database for backup as an *.sql file rather than only an individual table. On the localhost I have several databases with one named "foo" and it is that which I want to backup and not any of the individual tables inside the database "foo". The code to connect to the database; //Database Information $dbhost = "localhost"; $dbname = "foo"; $dbuser = "bar"; $dbpass = "rulz"; //Connect to database mysql_connect ($dbhost, $dbuser, $dbpass) or die("Could not connect: ".mysql_error()); mysql_select_db($dbname) or die(mysql_error()); The code to backup the database; // Grab the time to know when this post was submitted $time = date('Y-m-d-H-i-s'); $tableName = 'foo'; $backupFile = '/sql/backup/'. $time .'.sql'; $query = "SELECT * INTO OUTFILE '". $backupFile ."' FROM ". $tableName .""; $result = mysql_query($query)or die("Database query died: " . mysql_error()); My brain is hurting near to the end of the day so no doubts i've missed something out very obvious. Thanks in advance to anyone helping me out.

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• When software problems reported are not really software problems

  - by AndyUK

  Hi Apologies if this has already been covered or you think it really belongs on wiki. I am a software developer at a company that manufactures microarray printing machines for the biosciences industry. I am primarily involved in interfacing with various bits of hardware (pneumatics, hydraulics, stepper motors, sensors etc) via GUI development in C++ to aspirate and print samples onto microarray slides. On joining the company I noticed that whenever there was a hardware-related problem this would cause the whole setup to freeze, with nobody being any the wiser as to what the specific problem was - hardware / software / misuse etc. Since then I have improved things somewhat by introducing software timeouts and exception handling to better identify and deal with any hardware-related problems that arise eg PLC commands not successfully completed, inappropriate FPGA response commands, and various other deadlock type conditions etc. In addition, the software will now log a summary of the specific problem, inform the user and exit the thread gracefully. This software is not embedded, just interfacing using serial ports. In spite of what has been achieved, non-software guys still do not fully appreciate that in these cases, the 'software' problem they are reporting to me is not really a software problem, rather the software is reporting a problem, but not causing it. Don't get me wrong, there is nothing I enjoy more than to come down on software bugs like a ton of bricks, and looking at ways of improving robustness in any way. I know the system well enough now that I almost have a sixth sense for these things. No matter how many times I try to explain this point to people, it does not really penetrate. They still report what are essentially hardware problems (which eventually get fixed) as software ones. I would like to hear from any others that have endured similar finger-pointing experiences and what methods they used to deal with them.

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• uiview's controls unresponsive.. or how to foul up a view hierarchy

  - by user293139

  Hello all, I'm working on an app that has two sections, a config section and a results section. My config section needs to be 2 separate views (horizontal and vert, and yes, I can hear the intake of breath from here), with one rotatable view for the results. b/c of layout restraints and a lot of pain around rotation, I'm not using a navigation controller. I've been experiencing the joys of rotation experimentation and have settled upon keeping my views contained as subviews of my view controller. i.e. view controller.view.subviews = configH, configV, and results. I then use the controller.view bringSubviewToFront to bring the either the configH, configV, or the result view to the front. Rotation works-queue(humor intended) the angelic choirs... almost. What's happening is that my configV button's are responsive, but when the device (or simulator) is rotated, my configH controls are not. (configV is the second subview added, but the first one to be brought to the front because app comes up in portrait mode) The controls on the results view also work. Plan B was to assign the controller.view to configH, configV, or results. All of my controls now work, but rotation is now fouled up. Question 1: Is there a better way to do this? (a horizontal and vertical config view and a rotatable results view) Question 2: Does the above suggest a design issue, or is it more likely that my addled brain is just missing something in my own code. (nothing from the peanut gallery please) many thanks!

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• A monkey could do this better - Access to and availability of private member functions in C++

  - by David

  I am wandering the desert of my brain. I'm trying to write something like the following: class MyClass { // Peripherally Related Stuff public: void TakeAnAction(int oneThing, int anotherThing) { switch(oneThing){ case THING_A: TakeThisActionWith(anotherThing); break; //cases THINGS_NOT_A: }; private: void TakeThisActionWith(int thing) { string outcome = new string; outcome = LookUpOutcome(thing); // Do some stuff based on outcome return; } string LookUpOutcome(int key) { string oc = new string; oc = MyPrivateMap[key]; return oc; } map<int, string> MyPrivateMap; Then in the .cc file where I am actually using these things, while compiling the TakeAnAction section, it [CC, the solaris compiler] throws an an error: 'The function LookUpOutcome must have a prototype' and bombs out. In my header file, I have declared 'string LookUpOutcome(int key);' in the private section of the class. I have tried all sorts of variations. I tried to use 'this' for a little while, and it gave me 'Can only use this in non-static member function.' Sadly, I haven't declared anything static and these are all, putatively, member functions. I tried it [on TakeAnAction and LookUp] when I got the error, but I got something like, 'Can't access MyPrivateMap from LookUp'. MyPrivateMap could be made public and I could refer to it directly, I guess, but my sensibility says that is not the right way to go about this [that means that namespace scoped helper functions are out, I think]. I also guess I could just inline the lookup and subsequent other stuff, but my line-o-meter goes on tilt. I'm trying desperately not to kludge it.

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• How much detail should be in a project plan or spec?

  - by DeanMc

  I have an issue that I feel many programmers can relate to... I have worked on many small scale projects. After my initial paper brain storm I tend to start coding. What I come up with is usually a rough working model of the actual application. I design in a disconnected fashion so I am talking about underlying code libraries, user interfaces are the last thing as the library usually dictates what is needed in the UI. As my projects get bigger I worry that so should my "spec" or design document. The above paragraph, from my investigations, is echoed all across the internet in one fashion or another. When a UI is concerned there is a bit more information but it is UI specific and does not relate to code libraries. What I am beginning to realise is that maybe code is code is code. It seems from my extensive research that there is no 1:1 mapping between a design document and the code. When I need to research a topic I dump information into OneNote and from there I prioritise features into versions and then into related chunks so that development runs in a fairly linear fashion, my tasks tend to look like so: Implement Binary File Reader Implement Binary File Writer Create Object to encapsulate Data for expression to the caller Now any programmer worth his salt is aware that between those three to do items could be a potential wall of code that could expand out to multiple files. I have tried to map the complete code process for each task but I simply don't think it can be done effectively. By the time one mangles pseudo code it is essentially code anyway so the time investment is negated. So my question is this: Am I right in assuming that the best documentation is the code itself. We are all in agreement that a high level overview is needed. How high should this be? Do you design to statement, class or concept level? What works for you?

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• How do I design a Wizard-based system with SoC in mind?

  - by Erik Forbes

  I'm building a Windows Forms system (in C# if it matters to anyone) that provides an application automation service. As this application is targeted at users who are not computer savvy, I've decided to break up the functions of the application into various tasks, and provide these tasks via a wizard UI. I'd like to avoid coupling the views and view engine (from which the Wizard will be built) to the automation engine. The problem I'm having is that the automation engine, which runs on a separate thread while it does its thing, needs to report status information back to the user, as well as listen for cancel or pause events from the user. Since I don't want the view engine or the automation engine to rely on each other, I'm having a hard time figuring out how to provide for this information conduit. Any insights into this issue I'm having would be greatly appreciated. I've been wracking my brain for a couple weeks now on this point, and I really don't want to give up and just couple everything together. If anyone needs additional details to help come up with some sort of idea please let me know and I'll be happy to provide them.

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• Python virtualenv questions

  - by orokusaki

  I'm using VirtualEnv on Windows XP. I'm wondering if I have my brain wrapped around it correctly. I ran virtualenv ENV and it created C:\WINDOWS\system32\ENV. I then changed my PATH variable to include C:\WINDOWS\system32\ENV\Scripts instead of C:\Python27\Scripts. Then, I checked out Django into C:\WINDOWS\system32\ENV\Lib\site-packages\django-trunk, updated my PYTHON_PATH variable to point the new Django directory, and continued to easy_install other things (which of course go into my new C:\WINDOWS\system32\ENV\Lib\site-packages directory). I understand why I should use VirtualEnv so I can run multiple versions of Django, and other libraries on the same machine, but does this mean that to switch between environments I have to basically change my PATH and PYTHON_PATH variable? So, I go from developing one Django project which uses Django 1.2 in an environment called ENV and then change my PATH and such so that I can use an environment called ENV2 which has the dev version of Django? Is that basically it, or is there some better way to automatically do all this (I could update my path in Python code, but that would require me to write machine-specific code in my application)? Also, how does this process compare to using VirtualEnv on Linux (I'm quite the beginner at Linux).

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• Recommendations to handle development and deployment of php web apps using shared project code

  - by Exception e

  I am wondering what the best way (for a lone developer) is to develop a project that depends on code of other projects deploy the resulting project to the server I am planning to put my code in svn, and have shared code as a separate project. There are problems with svn:externals which I cannot fully estimate. I've read subversion:externals considered to be an anti-pattern, and How do you organize your version control repository, but there is one special thing with php-projects (and other interpreted source code): there is no final executable resulting from your libraries. External dependencies are thus always on raw source code. Ideally I really want to be able to develop simultaneously on one project and the projects it dependends on. Possible way: Check out a projects' dependency in a sub folder as a working copy of the trunk. Problems I foresee: When you want to deploy a project, you might want to freeze its dependencies, right? The dependency code should not end up as a duplicate in the projects repository, I think. *(update1: I additionally assume svn:ignore will pose problems if I cannot fall back on symlinks, see my comment) I am still looking for suggestions that do not require the use junction points. They are a sort of unsupported hack in winxp, which may break some programs* This leads me to the last part of the question (as one has influence on the other): how do you deploy apps whith such dependencies? I've looked into BuildOut for Python, but it seems to be tightly related to the python ecosystem (resolving and fetching python modules from the web etc). I am very eager to learn about your best practices.

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• How do I fork correctly in a perl module for znc?

  - by rarbox

  I'm currently writing an IRC bot. The scripts are loaded as perl modules in ZNC but the bot gets disconnected with an Input/Output error if I create a forked process. This is a working example script without fork, but this causes the bot to freeze until the script finishes doing its task. package imdb; use warnings; use strict; sub new { my ($class) = @_; my $self = {}; bless( $self, $class ); return( $self ); } sub OnChanMsg { my ($self, $nick, $channel,$text) = @_; #unless (my $pid = fork()) { my $result = a_slow_process($text); ZNC::PutIRC( "PRIVMSG $channel :$result" ); # exit; #} return( ZNC::CONTINUE ); } sub OnShutdown { my ( $me ) = @_; } sub a_slow_process { my $input = shift; sleep 10; return "You said $input."; } 1; The fork code that is causing the error is commented out. How do I fix this? Edited to add: I was told that ZNC::PutIRC should not be put in the child process.

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• My jQuery and PHP give different results on the same thing?

  - by Stefan

  Hey all, Annoying brain numbing problem. I have two functions to check the length of a string (primarily, the js one truncates as well) heres the one in Javascript: $('textarea#itemdescription').keyup(function() { var charLength = $(this).val().length; // Displays count $('span#charCount').css({'color':'#666'}); $('span#charCount').html(255 - charLength); if($(this).val().length >= 240){ $('span#charCount').css({'color':'#FF0000'}); } // Alerts when 250 characters is reached if($(this).val().length >= 255){ $('span#charCount').css({'color':'#FF0000'}); $('span#charCount').html('<strong>0</strong>'); var text = $('textarea#itemdescription').val().substring(0,255) $('textarea#itemdescription').val(text); } }); And here is my PHP to double check: if(strlen($_POST["description"])>255){ echo "Description must be less than ".strlen($_POST["description"])." characters"; exit(); } I'm using jQuery Ajax to post the values from the textarea. However my php validation says the strlen() is longer than my js is essentially saying. So for example if i type a solid string and it says 0 or 3 chars left till 255. I then click save and the php gives me the length as being 261. Any ideas? Is it to do with special characters, bit sizes that js reads differently or misses out? Or is it to do with something else? Maybe its ill today!... :P Thanks, Stefan

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• Analyzing Web Application Speed

  - by Amy

  I'm a bit confused because the logical/programmer brain in me says that if all things are constant, the speed of a function must be constant. I am working on a PHP web application with jqGrid as a front end for showing the data. I am testing on my personal computer, so network traffic does not apply. I make an HTTP request to a PHP function, it returns the data, and then jqGrid renders it. What has me befuddled is that sometimes, Firebug reports that this is taking 300-600 milliseconds sometimes, and sometimes, it's taking 3.68 seconds. I can run the request over and over again, with very radically different response times. The query is the same. The number of users on the system is the same. No network latency. Same code. I'm not running other applications on the computer while testing. I could understand query caching improving performance on subsequent requests, but the speed is just fluctuating wildly with no rhyme or reason. So, my question is, what else can cause such variability in the response time? How can I determine what's doing it? More importantly, is there any way to get things more consistent?

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• How to display out the contents from mysql and path it to an image properly?

  - by Panda

  I was trying very hard to think of a solution for my problem but have drain all my brain cells into this...What happen is: I have a CK editor where it allows user to input both text and images. A good example would be http://ckeditor.com/demo. Something like the red riding good example in the demo. I would like to have text surrounding the image like the example. With CK editor, user can now do that. However, now they will submit the changes and i was wondering how should I save the data? What i have found: After reading my articles and solutions on the web, all the experts would advise not to put image into the mysql database together with the text. I would like to ask if this is the case what should I do to extract the text from the ck editor and store it into mysql database and separately store the images into my web server? I know how to retrieve text from mysql database. But how do you put the retrieved text abd images together such as it appears to be how the user have input in CK editor?? Guys I am sorry if my question is confusing you or is making you angry because i admit I am really a newbie in this and I will learn all that I can...Thanks for all your advice and teachings.

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• White Screen of Death (WSOD) in Browser

  - by nickyt

  Here's the specs: ASP.NET 3.5 using ASP.NET AJAX AJAX Control Toolkit jQuery 1.3.2 web services IIS6 on Windows Server 2003 SP1 SP1 SQLServer 2005 SP3 Site is SSL Here's the problem: I'm getting the White Screen of Death (WSOD) in pretty much any browser (at least FireFox and IE 7/8). We have an application that uses one popup window for updating records. Most of the time when you click on the [Edit] button to edit a record, the popup window opens and loads the update page. However, after editing records for a while, all of a sudden the popup window will open, but it stays blank and just hangs. The URL is in the address bar. Loading up Fiddler I noticed that the request for the update page is never sent which leads me to believe it's some kind of lockup on the client-side. If I copy the same URL that's in the popup window into a new browser window, the page generally loads fine. Observations: - Since the request is never sent to the server, it's definitely something client-side - Only appears to happen when there is some semblance of traffic on the site which is weird because this appears to be contained within client-side code - There is a web service being called in the background every few seconds checking if the user is logged on, but this doesn't cause the freeze. I'm really at a loss here. I've googled WSOD but not much seems to appear related to my specific WSOD. Any ideas?

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• How do I interact with a Perl object that has a hash attribute?

  - by brydgesk

  I have a class with several variables, one of which is a hash (_runs): sub new { my ($class, $name) = @_; my $self = { _name => $name, ... _runs => (), _times => [], ... }; bless ($self, $class); return $self; } Now, all I'm trying to do is create an accessor/mutator, as well as another subroutine that pushes new data into the hash. But I'm having a hell of a time getting all the referencing/dereferencing/$self calls working together. I've about burned my eyes out with "Can't use string ("blah") as a HASH ref etc etc" errors. For the accessor, what is 'best practice' for returning hashes? Which one of these options should I be using (if any)?: return $self->{_runs}; return %{ $self->{_runs} }; return \$self->{_runs}; Further, when I'm using the hash within other subroutines in the class, what syntax do I use to copy it? my @runs = $self->{_runs}; my @runs = %{ $self->{_runs} }; my @runs = $%{ $self->{_runs} }; my @runs = $$self->{_runs}; Same goes for iterating over the keys: foreach my $dt (keys $self->{_runs}) foreach my $dt (keys %{ $self->{_runs} }) And how about actually adding the data? $self->{_runs}{$dt} = $duration; %{ $self->{_runs} }{$dt} = $duration; $$self->{_runs}{$dt} = $duration; You get the point. I've been reading articles about using classes, and articles about referencing and dereferencing, but I can't seem to get my brain to combine the knowledge and use both at the same time. I got my _times array working finally, but mimicking my array syntax over to hashes didn't work.

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• Scope of "library" methods

  - by JS

  Hello, I'm apparently laboring under a poor understanding of Python scoping. Perhaps you can help. Background: I'm using the 'if name in "main"' construct to perform "self-tests" in my module(s). Each self test makes calls to the various public methods and prints their results for visual checking as I develop the modules. To keep things "purdy" and manageable, I've created a small method to simplify the testing of method calls: def pprint_vars(var_in): print("%s = '%s'" % (var_in, eval(var_in))) Calling pprint_vars with: pprint_vars('some_variable_name') prints: some_variable_name = 'foo' All fine and good. Problem statement: Not happy to just KISS, I had the brain-drizzle to move my handy-dandy 'pprint_vars' method into a separate file named 'debug_tools.py' and simply import 'debug_tools' whenever I wanted access to 'pprint_vars'. Here's where things fall apart. I would expect import debug_tools foo = bar debug_tools.pprint_vars('foo') to continue working its magic and print: foo = 'bar' Instead, it greets me with: NameError: name 'some_var' is not defined Irrational belief: I believed (apparently mistakenly) that import puts imported methods (more or less) "inline" with the code, and thus the variable scoping rules would remain similar to if the method were defined inline. Plea for help: Can someone please correct my (mis)understanding of scoping regards imports? Thanks, JS

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• C++ & proper TDD

  - by Kotti

  Hi! I recently tried developing a small-sized project in C# and during the whole project our team used the Test-Driven-Development (TDD) technique (xunit, moq). I really think this was awesome, because (when paired with C#) this approach allowed to relax when coding, relax when projecting and relax when refactoring. I suspect that all this TDD-stuff actually simplifies the coding process and, well, it allowed (eventually, for me) to get the same result with fewer brain cells working. Right after that I tried using TDD paired with C++ (I used Google Test and Google Mock libraries), and, I don't know why but I actually think that TDD here was a step back in terms of rapid application development. I had some moments when I had to spend huge amounts of time thinking of my tests, building proper mocks, rebuilding them and swearing at my monitor. And, well, I obviously can't ask something like "what I did wrong?" or "what was wrong in my approach?", because I don't know what to describe. But if there are any people who are used to TDD in C++ (and, probably C#) too, could you please advise me how to do this properly. Framework recommendations, architecture approaches, plain coding advices - if you are experienced in TDD & C++, please respond.

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• Why are symbols not frozen strings?

  - by Alex Chaffee

  I understand the theoretical difference between Strings and Symbols. I understand that Symbols are meant to represent a concept or a name or an identifier or a label or a key, and Strings are a bag of characters. I understand that Strings are mutable and transient, where Symbols are immutable and permanent. I even like how Symbols look different from Strings in my text editor. What bothers me is that practically speaking, Symbols are so similar to Strings that the fact that they're not implemented as Strings causes a lot of headaches. They don't even support duck-typing or implicit coercion, unlike the other famous "the same but different" couple, Float and Fixnum. The mere existence of HashWithIndifferentAccess, and its rampant use in Rails and other frameworks, demonstrates that there's a problem here, an itch that needs to be scratched. Can anyone tell me a practical reason why Symbols should not be frozen Strings? Other than "because that's how it's always been done" (historical) or "because symbols are not strings" (begging the question). Consider the following astonishing behavior: :apple == "apple" #=> false, should be true :apple.hash == "apple".hash #=> false, should be true {apples: 10}["apples"] #=> nil, should be 10 {"apples" => 10}[:apples] #=> nil, should be 10 :apple.object_id == "apple".object_id #=> false, but that's actually fine All it would take to make the next generation of Rubyists less confused is this: class Symbol < String def initialize *args super self.freeze end (and a lot of other library-level hacking, but still, not too complicated) See also: http://onestepback.org/index.cgi/Tech/Ruby/SymbolsAreNotImmutableStrings.red http://www.randomhacks.net/articles/2007/01/20/13-ways-of-looking-at-a-ruby-symbol Why does my code break when using a hash symbol, instead of a hash string? Why use symbols as hash keys in Ruby? What are symbols and how do we use them? Ruby Symbols vs Strings in Hashes Can't get the hang of symbols in Ruby

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• How is a referencing environment generally implemented for closures?

  - by Alexandr Kurilin

  Let's say I have a statically/lexically scoped language with deep binding and I create a closure. The closure will consist of the statements I want executed plus the so called referencing environment, or, to quote this post, the collection of variables which can be used. What does this referencing environment actually look like implementation-wise? I was recently reading about ObjectiveC's implementation of blocks, and the author suggests that behind the scenes you get a copy of all of the variables on the stack and also of all the references to heap objects. The explanation claims that you get a "snapshot" of the referencing environment at the point in time of the closure's creation. Is that more or less what happens, or did I misread that? Is anything done to "freeze" a separate copy of the heap objects, or is it safe to assume that if they get modified between closure creation and the closure executing, the closure will no longer be operating on the original version of the object? If indeed there's copying being made, are there memory usage considerations in situations where one might want to create plenty of closures and store them somewhere? I think that misunderstanding of some of these concepts might lead to tricky issues like the ones Eric Lippert mentions in this blog post. It's interesting because you'd think that it wouldn't make sense to keep a reference to a value type that might be gone by the time the closure is called, but I'm guessing that in C# the compiler will figure out that the variable is needed later and put it into the heap instead. It seems that in most memory-managed languages everything is a reference and thus ObjectiveC is a somewhat unique situation with having to deal with copying what's on the stack.

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• how to create a mootools 1.1 function with array

  - by liz

  i have a series of select lists, that i am using to populate text boxes with ids. so you click a select option and another text box is filled with its id. with just one select/id pair this works fine, but i have multiples, and the only thing that changes is the id of the select and input.. in fact just the ending changes, the inputs all start with featredproductid and the select ids all start with recipesproduct and then both end with the category. i know that listing this over and over for each category is not the way to do it. i think i need to make an array of the categories var cats = ['olive oil', "grains", "pasta"] and then use a forEach function? maybe? here is the clunky code window.addEvent('domready', function() { $('recipesproductoliveoil').addEvent('change', function(e){ pidselected = this.options[this.selectedIndex].getProperty('value') ; $("featuredproductidoliveoil").setProperties({ value: pidselected}); ; }); $('recipesproductgrains').addEvent('change', function(e){ pidselected = this.options[this.selectedIndex].getProperty('value') ; $("featuredproductidgrains").setProperties({ value: pidselected}); ; }); $('recipesproductpasta').addEvent('change', function(e){ pidselected = this.options[this.selectedIndex].getProperty('value') ; $("featuredproductidpasta").setProperties({ value: pidselected}); ; }); $('recipesproductpantry').addEvent('change', function(e){ pidselected = this.options[this.selectedIndex].getProperty('value') ; $("featuredproductidpantry").setProperties({ value: pidselected}); ; }); }); keep in mind this is mootools 1.1 (no i cant update it sorry). i am sure this is kind of basic, something i seem to have wrapping my brain around. but i am quite sure doing it as above is not really good...

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• Perl - Using hashes in classes

  - by brydgesk

  I have a class with several variables, one of which is a hash (_runs): sub new { my ($class, $name) = @_; my $self = { _name => $name, ... _runs => (), _times => [], ... }; bless ($self, $class); return $self; } Now, all I'm trying to do is create an accessor/mutator, as well as another subroutine that pushes new data into the hash. But I'm having a hell of a time getting all the referencing/dereferencing/$self calls working together. I've about burned my eyes out with "Can't use string ("blah") as a HASH ref etc etc" errors. For the accessor, what is 'best practice' for returning hashes? Which one of these options should I be using (if any)?: return $self->{_runs}; return %{ $self->{_runs} }; return \$self->{_runs}; Further, when I'm using the hash within other subroutines in the class, what syntax do I use to copy it? my @runs = $self->{_runs}; my @runs = %{ $self->{_runs} }; my @runs = $%{ $self->{_runs} }; my @runs = $$self->{_runs}; Same goes for iterating over the keys: foreach my $dt (keys $self->{_runs}) foreach my $dt (keys %{ $self->{_runs} }) And how about actually adding the data? $self->{_runs}{$dt} = $duration; %{ $self->{_runs} }{$dt} = $duration; $$self->{_runs}{$dt} = $duration; You get the point. I've been reading articles about using classes, and articles about referencing and dereferencing, but I can't seem to get my brain to combine the knowledge and use both at the same time. I got my _times array working finally, but mimicking my array syntax over to hashes didn't work.

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• Get the last checked checkboxes...

  - by Sara

  Hi everyone, I'm not sure how to accomplish this issue which has been confusing me for a few days. I have a form that updates a user record in MySQL when a checkbox is checked. Now, this is how my form does this: if (isset($_POST['Update'])) { $paymentr = $_POST['paymentr']; //put checkboxes array into variable $paymentr2 = implode(', ', $paymentr); //implode array for mysql $query = "UPDATE transactions SET paymentreceived=NULL"; $result = mysql_query($query); $query = "UPDATE transactions SET paymentdate='0000-00-00'"; $result = mysql_query($query); $query = "UPDATE transactions SET paymentreceived='Yes' WHERE id IN ($paymentr2)"; $result = mysql_query($query); $query = "UPDATE transactions SET paymentdate=NOW() WHERE id IN ($paymentr2)"; $result = mysql_query($query); foreach ($paymentr as $v) { //should collect last updated records and put them into variable for emailing. $query = "SELECT id, refid, affid FROM transactions WHERE id = '$v'"; $result = mysql_query($query) or die("Query Failed: ".mysql_errno()." - ".mysql_error()."<BR>\n$query<BR>\n"); $trans = mysql_fetch_array($result, MYSQL_ASSOC); $transactions .= '<br>User ID:'.$trans['id'].' -- '.$trans['refid'].' -- '.$trans['affid'].'<br>'; } } Unfortunately, it then updates ALL the user records with the latest date which is not what I want it to do. The alternative I thought of was, via Javascript, giving the checkbox a value that would be dynamically updated when the user selected it. Then, only THOSE checkboxes would be put into the array. Is this possible? Is there a better solution? I'm not even sure I could wrap my brain around how to do that WITH Javascript. Does the answer perhaps lie in how my mysql code is written? Thanks - I sincerely appreciate it!!!

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