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• Event handling for keyboard strokes

  - by david

  Hey, I'm trying to get familiar with the whole keyboard event detection thing. Here's my sample code. <fx:Script> <![CDATA[ import flash.events.KeyboardEvent; import mx.controls.Alert; private function init():void{ addEventListener(KeyboardEvent.KEY_DOWN,reportKeyDown); } private function reportKeyDown(event:KeyboardEvent):void { Alert.show("a key was pressed"); } ]]> </fx:Script> As you can see, I'm at stage 0 of playing around with it, but it won't work. Anyone has any idea what I should be doing instead? Thanks

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• Python Error-Checking Standard Practice

  - by chaindriver

  Hi, I have a question regarding error checking in Python. Let's say I have a function that takes a file path as an input: def myFunction(filepath): infile = open(filepath) #etc etc... One possible precondition would be that the file should exist. There are a few possible ways to check for this precondition, and I'm just wondering what's the best way to do it. i) Check with an if-statement: if not os.path.exists(filepath): raise IOException('File does not exist: %s' % filepath) This is the way that I would usually do it, though the same IOException would be raised by Python if the file does not exist, even if I don't raise it. ii) Use assert to check for the precondition: assert os.path.exists(filepath), 'File does not exist: %s' % filepath Using asserts seems to be the "standard" way of checking for pre/postconditions, so I am tempted to use these. However, it is possible that these asserts are turned off when the -o flag is used during execution, which means that this check might potentially be turned off and that seems risky. iii) Don't handle the precondition at all This is because if filepath does not exist, there will be an exception generated anyway and the exception message is detailed enough for user to know that the file does not exist I'm just wondering which of the above is the standard practice that I should use for my codes.

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• How to show why "try" failed in python

  - by calccrypto

  is there anyway to show why a "try" failed, and skipped to "except", without writing out all the possible errors by hand, and without ending the program? example: try: 1/0 except: someway to show "Traceback (most recent call last): File "<pyshell#0>", line 1, in <module> 1/0 ZeroDivisionError: integer division or modulo by zero" i dont want to doif:print error 1, elif: print error 2, elif: etc.... i want to see the error that would be shown had try not been there

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• How to determine whether a .NET exception is being handled?

  - by romkyns

  We're investigating a coding pattern in C# in which we'd like to use a "using" clause with a special class, whose Dispose() method does different things depending on whether the "using" body was exited normally or with an exception. To the best of my understanding, the CLR keeps track of the current exception being handled until it's been consumed by a "catch" handler. However it's not entirely clear whether this information is exposed in any way for the code to access. Do you know whether it is, and if so, how to access it? For example: using (var x = new MyObject()) { x.DoSomething(); x.DoMoreThings(); } class MyObject : IDisposable { public void Dispose() { if (ExceptionIsBeingHandled) Rollback(); else Commit(); } } This looks almost like System.Transactions.TransactionScope, except that success/failure is not determined by a call to x.Complete(), but rather based on whether the using body was exited normally.

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• Bluetooth in Java Mobile: Handling connections that go out of range

  - by Albus Dumbledore

  I am trying to implement a server-client connection over the spp. After initializing the server, I start a thread that first listens for clients and then receives data from them. It looks like that: public final void run() { while (alive) { try { /* * Await client connection */ System.out.println("Awaiting client connection..."); client = server.acceptAndOpen(); /* * Start receiving data */ int read; byte[] buffer = new byte[128]; DataInputStream receive = client.openDataInputStream(); try { while ((read = receive.read(buffer)) > 0) { System.out.println("[Recieved]: " + new String(buffer, 0, read)); if (!alive) { return; } } } finally { System.out.println("Closing connection..."); receive.close(); } } catch (IOException e){ e.printStackTrace(); } } } It's working fine for I am able to receive messages. What's troubling me is how would the thread eventually die when a device goes out of range? Firstly, the call to receive.read(buffer) blocks so that the thread waits until it receives any data. If the device goes out of range, it would never proceed onward to check if meanwhile it has been interrupted. Secondly, it would never close the connection, i.e. the server would not accept the device once it goes back in range. Thanks! Any ideas would be highly appreciated! Merry Christmas!

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• How can I dynamically inject code into event handlers in Delphi?

  - by mjustin

  For debugging / performance tests I would like to dynamically add logging code to all event handlers of components of a given type. For example, for all Dataset components located ona TDatamodule, I would like to add some code for the BeforeOpen and the AfterOpen event to store the start and end time and send a line to a logger with the elapsed time in the AfterOpen event. I would prefer to do this dynamically (no component subclassing), so that I can add this to all existing datamodules and forms with minimal effort only when needed. Iterating all components and filtering by their type is easy, but for the components which already have event handlers assigned, I need a way to store the existing event handlers, and assign a new modified event handler which first does the logging and then will invoke the original code which was already present. Is there a design pattern which can be applied, or even some example code which shows how to implement this in Delphi?

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• C# async callback on disposed form

  - by Rodney Burton

  Quick question: One of my forms in my winform app (c#) makes an async call to a WCF service to get some data. If the form happens to close before the callback happens, it crashes with an error about accessing a disposed object. What's the correct way to check/handle this situation? The error happens on the Invoke call to the method to update my form, but I can't drill down to the inner exception because it says the code has been optimized. The Code: public void RequestUserPhoto(int userID) { WCF.Service.BeginGetUserPhoto(userID, new AsyncCallback(GetUserPhotoCB), userID); } public void GetUserPhotoCB(IAsyncResult result) { var photo = WCF.Service.EndGetUserPhoto(result); int userID = (int)result.AsyncState; UpdateUserPhoto(userID, photo); } public delegate void UpdateUserPhotoDelegate(int userID, Binary photo); public void UpdateUserPhoto(int userID, Binary photo) { if (InvokeRequired) { var d = new UpdateUserPhotoDelegate(UpdateUserPhoto); Invoke(d, new object[] { userID, photo }); } else { if (photo != null) { var ms = new MemoryStream(photo.ToArray()); var bmp = new System.Drawing.Bitmap(ms); if (userID == theForm.AuthUserID) { pbMyPhoto.BackgroundImage = bmp; } else { pbPhoto.BackgroundImage = bmp; } } } }

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• Using jQuery's animate(), if the clicked on element is "<a href="#" ...> </a>", the fucntion should

  - by Jian Lin

  I was reading jQuery's page for animate() http://api.jquery.com/animate/ Its examples don't mention about if using <a href="#" id="clickme">click me</a> ... $('#clickme').click(function() { $('#someDiv').animate({left: "+=60"}); }) we actually still have to return false like in the old days? $('#clickme').click(function() { $('#someDiv').animate({left: "+=60"}); return false; }) (but then, those examples didn't use a <a> for the "click me"... but used something else. Otherwise the page will jump back to the beginning of the page? Does jQuery have a more elegant or magical way of doing it?

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• How to display a generic error page in Asp.Net MVC 2

  - by Picflight

  I have the following in my base controller: protected override void OnException(ExceptionContext filterContext) { if (filterContext == null) { throw new ArgumentNullException("filterContext"); } // If custom errors are disabled, we need to let the normal ASP.NET exception handler // execute so that the user can see useful debugging information. if (filterContext.ExceptionHandled || !filterContext.HttpContext.IsCustomErrorEnabled) { return; } Exception exception = filterContext.Exception; // If this is not an HTTP 500 (for example, if somebody throws an HTTP 404 from an action method), // ignore it. if (new HttpException(null, exception).GetHttpCode() != 500) { return; } // TODO: What is the namespace for ExceptionType? //if (!ExceptionType.IsInstanceOfType(exception)) //{ // return; //} // Send Email MailException(exception); // TODO: What does this line do? base.OnException(filterContext); filterContext.Result = new ViewResult { ViewName = "Error" }; filterContext.ExceptionHandled = true; filterContext.HttpContext.Response.Clear(); filterContext.HttpContext.Response.StatusCode = 500; } In my Shared folder, I have an Error.aspx View. Web.config <customErrors mode="On" /> I am still seeing the yellow screen when an exception occurs. What am I doing incorrectly?

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• Cleanly handling events

  - by nkr1pt

  I have code similar to this in all my observer classes that handle events fired by an event bus class. As you can see there are a lot of instanceof checks to choose the path of action needed to appropriately handle events, and I was wondering if this could be done more cleanly, eliminating the instanceof tests? @Override public void handleEvent(Event event) { if (event instanceof DownloadStartedEvent) { DownloadStartedEvent dsEvent = (DownloadStartedEvent)event; dsEvent.getDownloadCandidateItem().setState(new BusyDownloadingState()); } else if (event instanceof DownloadCompletedEvent) { DownloadCompletedEvent dcEvent = (DownloadCompletedEvent)event; dcEvent.getDownloadCandidateItem().setState(new FinishedDownloadingState()); DownloadCandidate downloadCandidate = dcEvent.getDownloadCandidateItem(). getDownloadCandidate(); if (downloadCandidate.isComplete()) { // start extracting } } else if (event instanceof DownloadFailedEvent) { DownloadFailedEvent dfEvent = (DownloadFailedEvent)event; dfEvent.getDownloadCandidateItem().setState(new FailedDownloadingState()); } }

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• Only variables can be passed by reference

  - by zaf

  I had the bright idea of using a custom error handler which led me down a rabbit hole. Following code gives (with and without custom error handler): Fatal error: Only variables can be passed by reference function foo(){ $b=array_pop(array("a","b","c")); return $b; } print_r(foo()); Following code gives (only with a custom error handler): (2048) Only variables should be passed by reference function foo(){ $a=explode( '/' , 'a/b/c'); $c=array_pop(array_slice($a,-2,1)); return $c; } print_r(foo()); The second one worries me since I have a lot of 'compact' code. So, I either ditch the bright idea of using a custom error handler (to improve my logging module) or expand all my code. Anyone with better ideas? Also, WTF?

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• Onclick not firing

  - by user320588

  I have a set of buttons on my master page (I have attached the code below) but no onclick event is being raised. I pulled the final page source and no onclick event was present. As you can see I tried a few different approaches to solve the problem. I am looking for a normal postback to the server but I am getting nothing when I click any of these buttons. What am I not doing? --Master --Master Code Behind Protected Sub Button_Command(ByVal sender As Object, ByVal e As CommandEventArgs) Handles btnCancel.Command, btnClear.Command Session("ButtonClicked") = e.CommandArgument End Sub Protected Sub Button_Click(ByVal sender As Object, ByVal e As EventArgs) Handles btnSave.Click, btnSubmit.Click Session("ButtonClicked") = CType(sender, Button).CommandArgument End Sub --Page Source

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• Visual Studio 2008's annoying auto-handling of block comments

  - by Dave

  I read that great post on Visual Studio 2008 annoyances, but didn't see this one. It drives me crazy. Now, I realize that some people use block comments like this for function documentation and the like: /* * * * */ But you know, this is VS2008 and now we can use ///. The only time I ever feel the need to use C-style commenting is when I have some junk or test code that I temporarily want to remove. It absolutely drives me nuts when I do the first /* and then when I add a line after the test code, it automatically puts a space after the * and I end up with this: * / . So then I end up always having to backspace to complete the block comment. I looked through all of the C# editor settings in the VS2008 IDE, and didn't find anything relevant. Does this drive anyone else here crazy, or am I turning into a codemudgeon?

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• How to Make my application handle Errors for a few different scenarios?

  - by NightsEVil

  so i have this code to extract a program to the temp directory then run it, the problem is it doesn't work perfectly on every computer (for some reason it hits a error or exception sometimes) string tempFolder = System.IO.Path.Combine(System.IO.Path.GetTempPath(), ""); System.Diagnostics.Process defrag1 = System.Diagnostics.Process.Start(@"Programs\Optimize\AusLogics_Defrag.exe", string.Format(" -o{0} -y", tempFolder)); defrag1.WaitForExit(); string executableDirectoryName = Path.GetDirectoryName(Application.ExecutablePath); System.Diagnostics.Process defrag2 = System.Diagnostics.Process.Start(tempFolder + "\\" + "AusLogics_Defrag" + "\\" + "DiskDefrag.exe", ""); defrag2.WaitForExit(); System.IO.Directory.Delete(tempFolder + "\\" + "AusLogics_Defrag", true); and what i wanna know is there a way that say if it starts to extract but hits a error (no matter what it is) it will automatically change and go to this code, but if it DOESN'T hit a error it continues as it was meant to? string tempFolder = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData); System.Diagnostics.Process defrag1 = System.Diagnostics.Process.Start(@"Programs\Optimize\AusLogics_Defrag.exe", string.Format(" -o{0} -y", tempFolder)); defrag1.WaitForExit(); string executableDirectoryName = Path.GetDirectoryName(Application.ExecutablePath); System.Diagnostics.Process defrag2 = System.Diagnostics.Process.Start(tempFolder + "\\" + "AusLogics_Defrag" + "\\" + "DiskDefrag.exe", ""); defrag2.WaitForExit(); System.IO.Directory.Delete(tempFolder + "\\" + "AusLogics_Defrag", true); with the path going to the application data folder? and if THAT hits a error it would change that path to this, but if it DOESN'T hit a error it continues as it was meant to? string tempFolder = System.Environment.GetEnvironmentVariable("HomeDrive");

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• Error handling in the RequestHandler without embedding in URI

  - by hyn

  When a user sends a filled form, I want to print an error message in case there is an input error. One of the GAE sample codes does this by embedding the error message in the URI. Inside the form handler (get): self.redirect('/compose?error_message=%s' % message) and in the handler (get) of redirected URI, gets the message from request: values = { 'error_message': self.request.get('error_message'), ... Is there a way to accomplish the same without embedding the message in the URI?

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• Eclipse And Linux: Keyboard unusable after gnome-screen-saver

  - by Martijn Courteaux

  Hi, I know this is not programming related. But I can't find any topics on Google or UbuntuForums. So the problem is: When gnome-screensaver starts on the moment Eclipse has the focus and I wake up again my laptop, Eclipse doesn't listen to keyboard-events. To solve this I have to change the focus to another program and then back to Eclipse. Than it works again. This isn't a real problem, but it would be nice if someone can solve it. Thanks

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• Checking for nil in view in Ruby on Rails

  - by seaneshbaugh

  I've been working with Rails for a while now and one thing I find myself constantly doing is checking to see if some attribute or object is nil in my view code before I display it. I'm starting to wonder if this is always the best idea. My rationale so far has been that since my application(s) rely on user input unexpected things can occur. If I've learned one thing from programming in general it's that users inputting things the programmer didn't think of is one of the biggest sources of run-time errors. By checking for nil values I'm hoping to sidestep that and have my views gracefully handle the problem. The thing is though I typically for various reasons have similar nil or invalid value checks in either my model or controller code. I wouldn't call it code duplication in the strictest sense, but it just doesn't seem very DRY. If I've already checked for nil objects in my controller is it okay if my view just assumes the object truly isn't nil? For attributes that can be nil that are displayed it makes sense to me to check every time, but for the objects themselves I'm not sure what is the best practice. Here's a simplified, but typical example of what I'm talking about: controller code def show @item = Item.find_by_id(params[:id]) @folders = Folder.find(:all, :order => 'display_order') if @item == nil or @item.folder == nil redirect_to(root_url) and return end end view code <% if @item != nil %> display the item's attributes here <% if @item.folder != nil %> <%= link_to @item.folder.name, folder_path(@item.folder) %> <% end %> <% else %> Oops! Looks like something went horribly wrong! <% end %> Is this a good idea or is it just silly?

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• How can I process a form's events in another class in VB.NET?

  - by CowKingDeluxe

  Here's my code: Public Class Form1 End Class Public Class Form1Handler Inherits Form1 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click MsgBox("I") End Sub End Class I'm trying to get Form1Handler to process Form1's events automatically. How can I do this? Should I use a module instead? I'm doing this in VB 2010.

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• How to catch specific exception without error number?

  - by CJ7

  I need to catch the following specific exception: System.Data.OleDb.OleDbException was caught ErrorCode=-2147467259 Message="The changes you requested to the table were not successful because they would create duplicate values in the index, primary key, or relationship. Change the data in the field or fields that contain duplicate data, remove the index, or redefine the index to permit duplicate entries and try again." Source="Microsoft JET Database Engine" I'm not sure what ErrorCode is but it looks unreliable. Can I rely on Message being identical across platforms? Is the only solution to do a text search of Message for words like duplicate and primary key? Note: see my question here for why I need to catch this exception.

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• Where do I handle asynchronous exceptions?

  - by Jurily

  Consider the following code: class Foo { // boring parts omitted private TcpClient socket; public void Connect(){ socket.BeginConnect(Host, Port, new AsyncCallback(cbConnect), quux); } private void cbConnect(IAsyncResult result){ // blah } } If socket throws an exception after BeginConnect returns and before cbConnect gets called, where does it pop up? Is it even allowed to throw in the background?

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• handling bluetooth spp pairing request thru app

  - by Mr. Kakakuwa Bird

  Hi My android application is in blueotooth SPP server mode and listening for client devices, my application knows the passcode required for pairing of that devices. My question is, Is it possible to handle pairing request through application. Thanks and Regards.

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• Catch a thread's exception in the caller thread in Python

  - by Mikee

  Hi Everyone, I'm very new to Python and multithreaded programming in general. Basically, I have a script that will copy files to another location. I would like this to be placed in another thread so I can output "...." to indicate that the script is still running. The problem that I am having is that if the files cannot be copied it will throw an exception. This is ok if running in the main thread; however, having the following code does not work: try: threadClass = TheThread(param1, param2, etc.) threadClass.start() ##### **Exception takes place here** except: print "Caught an exception" In the thread class itself, I tried to re-throw the exception, but it does not work. I have seen people on here ask similar questions, but they all seem to be doing something more specific than what I am trying to do (and I don't quite understand the solutions offered). I have seen people mention the usage of sys.exc_info(), however I do not know where or how to use it. All help is greatly appreciated! EDIT: The code for the thread class is below: class TheThread(threading.Thread): def __init__(self, sourceFolder, destFolder): threading.Thread.__init__(self) self.sourceFolder = sourceFolder self.destFolder = destFolder def run(self): try: shul.copytree(self.sourceFolder, self.destFolder) except: raise

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• Catching the Facebook Login Event to change the HTML of the parent page

  - by Arkid

  I am trying to create Facebook based login using Javascript. Once a person clicks a button he should get a div replaced by another div, if he is logged in to Facebook. However, if he is not logged in to Facebook he is asked his Facebook credentials and he logs in. However, we need the user to click the button once more for the div replacement to happen in this case. I want to know if there is a way in which I can catch the Facebook login event and change the div? Is polling a way or there is some other way out. I want to use only Javascript.

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• Rails: common approach for handling exceptions in restful actions on objects that have been destroye

  - by Greg

  It is very common in Rails for an objects_controller controller to have RESTful edit and destroy actions like so: def edit @object = Object.find(params[:id]) end def destroy @object = Object.find(params[:id]) @object.destroy redirect_to :back end With an associated view that provides edit and destroy links like so: <%= link_to "Edit the Object", edit_object_path(object) %> <%= link_to "Delete", object, :confirm => 'Are you sure?', :method => :delete %> And it is easy to blow this up. If I open two browser windows, A and B, destroy an object with the "Delete" link in browser A and then press the "Edit" link in browser B, the find() in the edit action throws an exception. Obviously there are several ways to deal with this in the edit action: catch the exception and recover gracefully use @object = find(:first, "conditions... etc. and test the @object before going further But seeing as this is such a common pattern, I would love to know how other folks deal with this situation.

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• Can you catch exceeded allocated memory error before it kills the script?

  - by kristovaher

  The thing is that I want to catch memory problems before they happen. I have a system that gets rows from database and casts the returned associative array to a variable, but I never know what the size of the database result is is or how much memory it will take once the database request is made. This means that my software can fail simply because memory is exceeded. But I want to avoid that somehow. One of the ways is to obviously make database requests that are smaller, but what if this is not possible or what if I do not know the size of data that is returned from database? Is it possible to 'catch' situations where memory use is exceeded in PHP? Something like this: $requestOk=memory_test(function(){ return doSomething(); }); if($requestOk){ // Memory seems fine // $requestOk now has the value from memory_test() function } else { // Function would have exceeded memory } I just find it problematic that my script can just die at any moment because of memory issues. From what I know, try-catch cannot be used here because it is a fatal error. Any help would be appreciated!

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