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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 to create custom exception handler for custom controls or extension methods.

    - by Shantanu Gupta
    I am creating an extension method in C# to retrieve some value from datagridview. Here if a user gives column name that doesnot exists then i want this function to throw an exception that can be handled at the place where this function will be called. How can i achieve this. public static T Value<T>(this DataGridView dgv, int RowNo, string ColName) { if (!dgv.Columns.Contains(ColName)) throw new ArgumentException("Column Name " + ColName + " doesnot exists in DataGridView."); return (T)Convert.ChangeType(dgv.Rows[RowNo].Cells[ColName].Value, typeof(T)); }

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  • How to get the current exception without having passing the variable?

    - by Pierre-Alain Vigeant
    I am looking for a way to retrieve the current exception without having to pass it as a variable. Suppose the following code public void MakeItFail() { try { throw new FailException(); } catch // Yes I'm aware that this shouldn't be done, but I don't want to go through all the code base and change it { ShowMessage("An error occured"); } } public void ShowMessage(string message) { // How can I retrieve the exception here } In the watch window, I can use $exception to get the current exception. Is there is a code equivalent?

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  • Very weird C file-handling anomaly

    - by KáGé
    Hello, I got a very weird issue that I cant figure out in my school project, which is the simulation of a simple filesystem in a human-readable textfile. Unfortunately I don't yet have enough time to translate the comments in my code or make it less gibberish, so if you are bothered by that, you don't have to help, I understand. See the code HERE. Now in drive.h, at line 574 is this part: i = getline(); #ifdef DEBUG printf("Free space in all found at %d.\n\n", i); if(drive.disk != NULL){ printf("Disk OK\n\n"); } #endif //write in data state = seekline(i); Before this it finds place for the allocation database entry in the ALL sector (see the "image files" in the mounts folder, this issue was tested on mount_30.efs-dbf), then gets the line with i = getline() fine (getline is in lglobal.h, line 39), but after that any file manipulation (in this case seekline's fseek, but if I comment that out, then the first fprintf after that) crashes the program straight away. I think the file gets somehow corrupted (though the Disk OK message appears) but can't figure out how. I've tried putting i = getline(); into comment, but it didn't make any difference. I've also tried asking at local programming forums but they didn't really help either. The last few lines of the output before it crashes: Dir written. (drive.h line 562) Seekline entered: 268 (called at drive.h line 564) Getline entered. (called at drive.h line 574) Line got: 268. Free space in all found at 268. (drive.h line 576) Seekline entered: 268 (called at drive.h line 582, note that this exact call was run successfully less than 20 lines back. This one should set the pointer to the beginning of the line it is currently in) After this it crashes. Does anyone has any idea of what causes this and how could I fix it? Thank you.

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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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  • Linq to SQL - Error handling

    - by Sundararajan S
    I have a linq to sql statement that inserts records in the database. If there is a duplicate, it throws Primary key violation . after this happens, whenever i try to execute any other statement, it repeatedly shows this error. Is this a problem of transaction not getting closed. Also how to handle transactions in a more reliable way in LINQ to SQL

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  • Handling selection and deselection of objects in a user interface

    - by Dennis
    I'm writing a small audio application (in Silverlight, but that's not really relevant I suppose), and I'm a struggling with a problem I've faced before and never solved properly. This time I want to get it right. In the application there is one Arrangement control, which contains several Track controls, and every Track can contain AudioObject controls (these are all custom user controls). The user needs to be able to select audio objects, and when these objects are selected they are rendered differently. I can make this happen by hooking into the MouseDown event of the AudioObject control and setting state accordingly. So far so good, but when an audio object is selected, all other audio objects need to be deselected (well, unless the user holds the shift key). Audio objects don't know about other audio objects though, so they have no way to tell the rest to deselect themselves. Now if I would approach this problem like I did the last time I would pass a reference to the Arrangement control in the constructor of the AudioObject control and give the Arrangement control a DeselectAll() method or something like that, which would tell all Track controls to deselect all their AudioObject controls. This feels wrong, and if I apply this strategy to similar issues I'm afraid I will soon end up with every object having a reference to every other object, creating one big tightly coupled mess. It feels like opening the floodgates for poorly designed code. Is there a better way to handle this?

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  • .net layered design: return error code to forms indicating which controls have an error

    - by David Casillas
    Let's say I have a simple application. It tries to add a new entry to a database grabing the info from the user. The information is a tipical MasterDetail objetc like an invoice. The Invoice object used to collect the data has some simple atributes (Id, Date, etc...) and a List of InvoiceDetail, consisting of some simple atributes (invoiceId, productId, quantity, etc...) A form in the UI Layer collects the data from the user, creates an instance of Invoice and sends it to the Bussiness Layer. The Bussines layer sends the data to a Validation Module. If any error in the input is detected it has to return some kind of error code. The Bussiness Layer has to send the error code back to the Form to let the user correct the worng information. I want the application to display some kind of warning (a different background color for example) in every form control with an error. ¿What's a good aproach to I manage the errors to be able to inform the form which controls are wrong? ¿Can I create an error object?¿Use delegates?. I'm using VB.net but don't think this is relevant to the solution of the problem. P.D: Please suggest me some tags to this post.

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  • django handling file uploads - target different than media folder

    - by Tom Tom
    Hi, I want to enable the user to upload media which will not be saved in the media folder. When I use the following line of code data will be uploaded to media/upload/logo . logo_img = models.FileField(upload_to='upload/logo', blank=True) I'm wondering how I can change this behaviour. I would try to write a custom FileField and a view that serves the data based on the database entries. I do not want to place the data the user uploads to the media folder, since it is no public data. Is this approach correct? Are there solutions out there which do exactly what I want and I would reinvent the wheel with implementing this by myself? Would appreciate any help!

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  • Magento hiding all errors page.

    - by PankajK
    Magento Production version 1.2.1 store running on linux centos. I want to hide all error messages generating from Magento, or if error occurred then I want user to send to custom error page. I tried some solutions like putting Mage::setIsDeveloperMode(true); in index.php but it is not working properly, I even tried to set ini_set('display_errors', 0); but it is still not working. Magento still giving errors like "undefined index"

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  • How to break on unhandled exceptions in Silverlight

    - by Bruno Martinez
    In console .Net applications, the debugger breaks at the point of the throw (before stack unwinding) for exceptions with no matching catch block. It seems that Silverlight runs all user code inside a try catch, so the debugger never breaks. Instead, Application.UnhandledException is raised, but after catching the exception and unwinding the stack. To break when unhandled exceptions are thrown and not catched, I have to enable first chance exception breaks, which also stops the program for handled exceptions. Is there a way to remove the Silverlight try block, so that exceptions get directly to the debugger?

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  • Preventing EF4 ConstraintException when invoking TryUpdateModel

    - by twk
    Given following ASP.NET MVC controller code: [HttpPost] public ActionResult Create(FormCollection collection) { string[] whitelist = new []{ "CompanyName", "Address1", "Address2", ... }; Partner newPartner = new Partner(); if (TryUpdateModel(newPartner, whitelist, collection)) { var db = new mainEntities(); db.Partners.AddObject(newPartner); db.SaveChanges(); return RedirectToAction("Details/" + newPartner.ID); } else { return View(); } } The problem is with the Entity Framework 4: the example Partner entity is mapped to a database table with it's fields NOT ALLOWED to be NULL (which is ok by design - they're required). Unfortunately, invoking TryUpdateModel when some of the properties are nulls produces ConstraintException which is not expected! I do expect that TryUpdateModel return false in this case. It is ok that EF wouldn't allow set a property value to null if it should not be, but the TryUpdateMethod should handle that, and add the error to ModelState errors collection. I am wrong, or somebody screwed the implementation of TryUpdateModel method?

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  • Custom event listener on Android app

    - by Bilthon
    Hi everybody, I need to set up a simple event listener to refresh a listview from once in a while. The problem is I don't know how could I generate an event. I know that for events like key or button pressing I just need to implement the handler. But in this specific case I actually need to generate the event, which will be fired everytime another running thread of my app wakes up and refreshes it's list of news from a rss feed. I've done everything, but got stucked in here. Can I get any suggestion or link with some more info on how to implement this? Thanks Nelson R. Perez

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  • XSL file handling through javascript

    - by Zaid Iqbal
    i want to handle my xsl file through my javascript code. I made my XSL file but i want to dynamically change my XSL file at run time.As in add more attributes in header or data. My javascript code as follow` <script> function loadXMLDoc(dname) { if (window.XMLHttpRequest) { xhttp=new XMLHttpRequest(); } else { xhttp=new ActiveXObject("Microsoft.XMLHTTP"); } xhttp.open("GET",dname,false); xhttp.send(""); return xhttp.responseXML; } function displayResult() { xml=loadXMLDoc("cdcatalog.xml"); xsl=loadXMLDoc("cdcatalog.xsl"); // code for IE if (window.ActiveXObject) { ex=xml.transformNode(xsl); document.getElementById("example").innerHTML=ex; } // code for Mozilla, Firefox, Opera, etc. else if (document.implementation && document.implementation.createDocument) { xsltProcessor=new XSLTProcessor(); xsltProcessor.importStylesheet(xsl); resultDocument = xsltProcessor.transformToFragment(xml,document); document.getElementById("example").appendChild(resultDocument); } } </script> My XSL file code: <?xml version="1.0" encoding="ISO-8859-1"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:template match="/"> <html> <body> <h2>My CD Collection</h2> <table border="1"> <tr bgcolor="#9acd32"> <th align="left">Title</th> <th align="left">Artist</th> <th align="left">Country</th> </tr> <xsl:for-each select="catalog/cd"> <tr> <td><xsl:value-of select="title" /></td> <td><xsl:value-of select="artist" /></td> <td><xsl:value-of select="country" /></td> </tr> </xsl:for-each> </table> </body> </html> </xsl:template> </xsl:stylesheet> `

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  • What do programs see when ZFS can't deliver uncorrupted data?

    - by Jay Kominek
    Say my program attempts a read of a byte in a file on a ZFS filesystem. ZFS can locate a copy of the necessary block, but cannot locate any copy with a valid checksum (they're all corrupted, or the only disks present have corrupted copies). What does my program see, in terms of the return value from the read, and the byte it tried to read? And is there a way to influence the behavior (under Solaris, or any other ZFS-implementing OS), that is, force failure, or force success, with potentially corrupt data?

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  • Unable to turn off notice errors in PHP 5.3.2

    - by knkk
    Hi everyone, I recently migrated to PHP 5.3.2, and realized that I am unable to turn off notice errors in my site now. I went to php.ini, and in these lines: ; Common Values: ; E_ALL & ~E_NOTICE (Show all errors, except for notices and coding standards warnings.) ; E_ALL & ~E_NOTICE | E_STRICT (Show all errors, except for notices) ; E_COMPILE_ERROR|E_RECOVERABLE_ERROR|E_ERROR|E_CORE_ERROR (Show only errors) ; E_ALL | E_STRICT (Show all errors, warnings and notices including coding standards.) ; Default Value: E_ALL & ~E_NOTICE ; Development Value: E_ALL | E_STRICT ; Production Value: E_ALL & ~E_DEPRECATED ; http://php.net/error-reporting error_reporting = E_ALL & ~E_NOTICE ...I've tried setting everything (and I restart apache each time), but I am unable to get rid of notices. The only way I'm able to get rid of notice errors is by setting : display_errors = Off That is, of course, not something I can do since I need to see errors to fix them, and I would like to see errors on the webpage that I am coding rather than log them somewhere. Can someone help? Is this a bug in PHP 5.3.2 or something I am doing wrong? Thank you very much for your time! P. S. Also, would anyone know how I can get PHP 5.3.2 to support the .php3 extension?

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  • Memory section handling error

    - by Basilevs
    I'm getting a link time error: WARNING: /home/gulevich/development/camac-fedorov/camac/linux/k0607-lsi6/camac-k0607-lsi6.o (.ctors): unexpected non-allocatable section. Did you forget to use "ax"/"aw" in a .S file? Note that for example <linux/init.h> contains section definitions for use in .S files. The code causing the error (assembly in C source): # if defined(__ELF__) # define __SECTION_FLAGS ", \"aw\" , @progbits" /* writable flag needed for ld ".[cd]tors" sections bug workaround) */ # elif defined(__COFF__) # define __SECTION_FLAGS ", \"dr\"" /* untested, may be writable flag needed */ # endif asm ( ".section .ctors" __SECTION_FLAGS "\n" ".globl __ctors_begin__\n" "__ctors_begin__:\n" ".previous\n" ); Is there any way to fix this? The idea is to put a varaible __ctors_begin__ at the beginning of a certain memory section. This code is a legacy that worked fine using a different build system and older compiler. Meaning of this assembly code explained in an answer to my previous question.

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  • C# MessageBox Error Messages

    - by Jim Fell
    Hello. In my application I am using message boxes to display error information. try { // Something... } catch (SystemException ex) { MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); } This was fine at first, but as my program grows it becomes increasingly difficult to find the try-catch block where this error is generated. Is there a way to display the line of code or function in which the error was generated? I am using Microsoft Visual C# 2008 Express Edition. Thanks.

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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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  • 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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  • Pass string between two threads in java

    - by geeta
    I have to search a string in a file and write the matched lines to another file. I have a thread to read a file and a thread to write a file. I want to send the stringBuffer from read thread to write thread. Please help me to pass this. I amm getting null value passed. write thread: class OutputThread extends Thread{ /****************** Writes the line with search string to the output file *************/ Thread runner1,runner; File Out_File; public OutputThread() { } public OutputThread(Thread runner,File Out_File) { runner1 = new Thread(this,"writeThread"); // (1) Create a new thread. this.Out_File=Out_File; this.runner=runner; runner1.start(); // (2) Start the thread. } public void run() { try{ BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter(Out_File,true)); System.out.println("inside write"); synchronized(runner){ System.out.println("inside wait"); runner.wait(); } System.out.println("outside wait"); // bufferedWriter.write(line.toString()); Buffer Buf = new Buffer(); bufferedWriter.write(Buf.buffers); System.out.println(Buf.buffers); bufferedWriter.flush(); } catch(Exception e){ System.out.println(e); e.printStackTrace(); } } } Read Thraed: class FileThread extends Thread{ Thread runner; File dir; String search_string,stats; File Out_File,final_output; StringBuffer sb = new StringBuffer(); public FileThread() { } public FileThread(CountDownLatch latch,String threadName,File dir,String search_string,File Out_File,File final_output,String stats) { runner = new Thread(this, threadName); // (1) Create a new thread. this.dir=dir; this.search_string=search_string; this.Out_File=Out_File; this.stats=stats; this.final_output=final_output; this.latch=latch; runner.start(); // (2) Start the thread. } public void run() { try{ Enumeration entries; ZipFile zipFile; String source_file_name = dir.toString(); File Source_file = dir; String extension; OutputThread out = new OutputThread(runner,Out_File); int dotPos = source_file_name.lastIndexOf("."); extension = source_file_name.substring(dotPos+1); if(extension.equals("zip")) { zipFile = new ZipFile(source_file_name); entries = zipFile.entries(); while(entries.hasMoreElements()) { ZipEntry entry = (ZipEntry)entries.nextElement(); if(entry.isDirectory()) { (new File(entry.getName())).mkdir(); continue; } searchString(runner,entry.getName(),new BufferedInputStream(zipFile.getInputStream(entry)),Out_File,final_output,search_string,stats); } zipFile.close(); } else { searchString(runner,Source_file.toString(),new BufferedInputStream(new FileInputStream(Source_file)),Out_File,final_output,search_string,stats); } } catch(Exception e){ System.out.println(e); e.printStackTrace(); } } /********* Reads the Input Files and Searches for the String ******************************/ public void searchString(Thread runner,String Source_File,BufferedInputStream in,File output_file,File final_output,String search,String stats) { int count = 0; int countw = 0; int countl=0; String s; String[] str; String newLine = System.getProperty("line.separator"); try { BufferedReader br2 = new BufferedReader(new InputStreamReader(in)); //OutputFile outfile = new OutputFile(); BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(output_file,true)); Buffer Buf = new Buffer(); //StringBuffer sb = new StringBuffer(); StringBuffer sb1 = new StringBuffer(); while((s = br2.readLine()) != null ) { str = s.split(search); count = str.length-1; countw += count; if(s.contains(search)){ countl++; sb.append(s); sb.append(newLine); } if(countl%100==0) { System.out.println("inside count"); Buf.setBuffers(sb.toString()); sb.delete(0,sb.length()); System.out.println("outside notify"); synchronized(runner) { runner.notify(); } //outfile.WriteFile(sb,bufferedWriter); //sb.delete(0,sb.length()); } } } synchronized(runner) { runner.notify(); } br2.close(); in.close(); if(countw == 0) { System.out.println("Input File : "+Source_File ); System.out.println("Word not found"); System.exit(0); } else { System.out.println("Input File : "+Source_File ); System.out.println("Matched word count : "+countw ); System.out.println("Lines with Search String : "+countl); System.out.println("Output File : "+output_file.toString()); System.out.println(); } } catch(Exception e){ System.out.println(e); e.printStackTrace(); } } }

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  • Redundant code in exception handling

    - by Nicola Leoni
    Hi, I've a recurrent problem, I don't find an elegant solution to avoid the resource cleaning code duplication: resource allocation: try { f() } catch (...) { resource cleaning code; throw; } resource cleaning code; return rc; So, I know I can do a temporary class with cleaning up destructor, but I don't really like it because it breaks the code flow and I need to give the class the reference to the all stack vars to cleanup, the same problem with a function, and I don't figure out how does not exists an elegant solution to this recurring problem.

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