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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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  • Javascript onclick() event bubbling - working or not?

    - by user1071914
    I have a table in which the table row tag is decorated with an onclick() handler. If the row is clicked anywhere, it will load another page. In one of the elements on the row, is an anchor tag which also leads to another page. The desired behavior is that if they click on the link, "delete.html" is loaded. If they click anywhere else in the row, "edit.html" is loaded. The problem is that sometimes (according to users) both the link and the onclick() are fired at once, leading to a problem in the back end code. They swear they are not double-clicking. I don't know enough about Javascript event bubbling, handling and whatever to even know where to start with this bizarre problem, so I'm asking for help. Here's a fragment of the rendered page, showing the row with the embedded link and associated script tag. Any suggestions are welcomed: <tr id="tableRow_3339_0" class="odd"> <td class="l"></td> <td>PENDING</td> <td>Yabba Dabba Doo</td> <td>Fred Flintstone</td> <td> <a href="/delete.html?requestId=3339"> <div class="deleteButtonIcon"></div> </a> </td> <td class="r"></td> </tr> <script type="text/javascript">document.getElementById("tableRow_3339_0").onclick = function(event) { window.location = '//edit.html?requestId=3339'; };</script>

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  • Handling Types Defined in Plug-ins That Are No Longer Available

    - by Chris
    I am developing a .NET framework application that allows users to maintain and save "projects". A project can consist of components whose types are defined in the assemblies of the framework itself and/or in third-party assemblies that will be made available to the framework via a yet-to-be-built plug-in architecture. When a project is saved, it is simply binary-serialised to file. Projects are portable, so multiple users can load the same project into their own instances of the framework (just as different users may open the same MSWord document in their own local copies of MSWord). What's more, the plug-ins available to one user's framework might not be available to that of another. I need some way of ensuring that when a user attempts to open (i.e. deserialise) a project that includes a type whose defining assembly cannot be found (either because of a framework version incompatibility or the absence of a plug-in), the project still opens but the offending type is somehow substituted or omitted. Trouble is, the research I've done to date does not even hint at a suitable approach. Any ideas would be much appreciated, thanks.

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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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  • How to efficiently compare the sign of two floating-point values while handling negative zeros

    - by François Beaune
    Given two floating-point numbers, I'm looking for an efficient way to check if they have the same sign, given that if any of the two values is zero (+0.0 or -0.0), they should be considered to have the same sign. For instance, SameSign(1.0, 2.0) should return true SameSign(-1.0, -2.0) should return true SameSign(-1.0, 2.0) should return false SameSign(0.0, 1.0) should return true SameSign(0.0, -1.0) should return true SameSign(-0.0, 1.0) should return true SameSign(-0.0, -1.0) should return true A naive but correct implementation of SameSign in C++ would be: bool SameSign(float a, float b) { if (fabs(a) == 0.0f || fabs(b) == 0.0f) return true; return (a >= 0.0f) == (b >= 0.0f); } Assuming the IEEE floating-point model, here's a variant of SameSign that compiles to branchless code (at least with with Visual C++ 2008): bool SameSign(float a, float b) { int ia = binary_cast<int>(a); int ib = binary_cast<int>(b); int az = (ia & 0x7FFFFFFF) == 0; int bz = (ib & 0x7FFFFFFF) == 0; int ab = (ia ^ ib) >= 0; return (az | bz | ab) != 0; } with binary_cast defined as follow: template <typename Target, typename Source> inline Target binary_cast(Source s) { union { Source m_source; Target m_target; } u; u.m_source = s; return u.m_target; } I'm looking for two things: A faster, more efficient implementation of SameSign, using bit tricks, FPU tricks or even SSE intrinsics. An efficient extension of SameSign to three values.

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  • how to implement enhanced session handling in PHP

    - by praksant
    Hi, i'm working with sessions in PHP, and i have different applications on single domain. Problem is, that cookies are domain specific, and so session ids are sent to any page on single domain. (i don't know if there is a way to make cookies work in different way). So Session variables are visible in every page on this domain. I'm trying to implement custom session manager to overcome this behavior, but i'm not sure if i'm thinking about it right. I want to completely avoid PHP session system, and make a global object, which would store session data and on the end of script save it to database. On first access i would generate unique session_id and create a cookie On the end of script save session data with session_id, timestamps for start of session and last access, and data from $_SERVER, such as REMOTE_ADDR, REMOTE_PORT, HTTP_USER_AGENT. On every access chceck database for session_id sent in cookie from client, check IP, Port and user agent (for security) and read data into session variable (if not expired). If session_id expired, delete from database. That session variable would be implemented as singleton (i know i would get tight coupling with this class, but i don't know about better solution). I'm trying to get following benefits: Session variables invisible in another scripts on the same server and same domain Custom management of session expiration Way to see open sessions (something like list of online users) i'm not sure if i'm overlooking any disadvantages of this solution. Is there any better way? Thank you!!

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  • SQL Server stored procedure return code oddity

    - by gbn
    Hello The client that calls this code is restricted and can only deal with return codes from stored procs. So, we modified our usual contract to RETURN -1 on error and default to RETURN 0 if no error If the code hits the inner catch block, then the RETURN code default to -4. Where does this come from, does anyone know...? IF OBJECT_ID('dbo.foo') IS NOT NULL DROP TABLE dbo.foo GO CREATE TABLE dbo.foo ( KeyCol char(12) NOT NULL, ValueCol xml NOT NULL, Comment varchar(1000) NULL, CONSTRAINT PK_foo PRIMARY KEY CLUSTERED (KeyCol) ) GO IF OBJECT_ID('dbo.bar') IS NOT NULL DROP PROCEDURE dbo.bar GO CREATE PROCEDURE dbo.bar @Key char(12), @Value xml, @Comment varchar(1000) AS SET NOCOUNT ON DECLARE @StartTranCount tinyint; BEGIN TRY SELECT @StartTranCount = @@TRANCOUNT; IF @StartTranCount = 0 BEGIN TRAN; BEGIN TRY --SELECT @StartTranCount = 'fish' INSERT dbo.foo (KeyCol, ValueCol, Comment) VALUES (@Key, @Value, @Comment); END TRY BEGIN CATCH IF ERROR_NUMBER() = 2627 --PK violation UPDATE dbo.foo SET ValueCol = @Value, Comment = @Comment WHERE KeyCol = @Key; ELSE RAISERROR ('Tits up', 16, 1); END CATCH IF @StartTranCount = 0 COMMIT TRAN; END TRY BEGIN CATCH IF @StartTranCount = 0 AND XACT_STATE() <> 0 ROLLBACK TRAN; RETURN -1 END CATCH --Without this, we'll send -4 if we hit the UPDATE CATCH block above --RETURN 0 GO --Run with RETURN 0 and fish line commented out DECLARE @rtn int EXEC @rtn = dbo.bar 'abcdefghijkl', '<foobar />', 'testing' SELECT @rtn; SELECT * FROM dbo.foo DECLARE @rtn int EXEC @rtn = dbo.bar 'abcdefghijkl', '<foobar2 />', 'testing2' --updated OK but we get @rtn = -4 SELECT @rtn; SELECT * FROM dbo.foo --uncomment fish line DECLARE @rtn int EXEC @rtn = dbo.bar 'abcdefghijkl', '<foobar />', 'testing' --Hit outer CATCH, @rtn = -1 as expected SELECT @rtn; SELECT * FROM dbo.foo

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  • Exception handling in Linq to SQL for customers without orders

    - by stackoverflowuser
    I have the following code to retrieve customer name, total (orders ), sum (order details) for reach customer in Northwind database. The problem with below code is that it raises an exception since a few customers dont have any entry in orders table. I know using the query syntax (join) the exception can be avoided. I want to know if the same can be handled with the extension method syntax. var customerOrders = db.Customers .Select(c => new { CompanyName = c.CompanyName, TotalOrders = c.Orders.Count(), TotalQuantity = c.Orders .SelectMany(o => o.Order_Details).Sum(o=>o.Quantity) });

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  • Avoid throwing a new exception

    - by GustlyWind
    I have an if condition which checks for value and the it throws new NumberFormatException Is there any other way to code this if (foo) { throw new NumberFormatException } // .. catch (NumberFormatException exc) { // some msg... }

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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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  • Catching errors in ANTLR and finding parent

    - by Andreas
    I have found out that I can catch errors during parsing by overwriting displayRecognitionError, but how do I find the parent "node" of this error? ex. if I have the grammar: prog: stat expr; stat: STRING; expr: INTEGER; And give it the input "abc def". Then I will get an error at "def" which should be an integer. At this point I then want to get the parent which is "expr" (since it fails inside the INTEGER part) and it's parent "prog". Kind of like printing stack trace in java. I tried to look at the node from RecognitionException parsed to displayRecognitionError, but it is null, and using CommonErrorNode the parent is null. Should I maybe take a completely different approach?

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  • Catching error caused by InitialContext.lookup

    - by Martin Schröder
    I'm developing a command line client (Java SE6) that now needs to talk to a Glassfish 2.1 server. The code for setting up this connection is try { final InitialContext context = new InitialContext(); final String ejbName = GeneratorCancelledRemote.class.getName(); generatorCancelled = (GeneratorCancelledRemote) context.lookup(ejbName); } catch (Throwable t) { System.err.println("--> Could not call server:"); t.printStackTrace(System.err); runWithOutEJB = true; } I'm now testing it without a running server and the client (when run from Eclipse 4.2) just bombs with 31.10.2012 10:40:09 com.sun.corba.ee.impl.transport.SocketOrChannelConnectionImpl WARNUNG: "IOP00410201: (COMM_FAILURE) Connection failure: socketType: IIOP_CLEAR_TEXT; hostname: localhost; port: 3700" org.omg.CORBA.COMM_FAILURE: vmcid: SUN minor code: 201 completed: No at com.sun.corba.ee.impl.logging.ORBUtilSystemException.connectFailure(ORBUtilSystemException.java:2783) at com.sun.corba.ee.impl.logging.ORBUtilSystemException.connectFailure(ORBUtilSystemException.java:2804) at com.sun.corba.ee.impl.transport.SocketOrChannelConnectionImpl.(SocketOrChannelConnectionImpl.java:261) at com.sun.corba.ee.impl.transport.SocketOrChannelConnectionImpl.(SocketOrChannelConnectionImpl.java:274) at com.sun.corba.ee.impl.transport.SocketOrChannelContactInfoImpl.createConnection(SocketOrChannelContactInfoImpl.java:130) at com.sun.corba.ee.impl.protocol.CorbaClientRequestDispatcherImpl.beginRequest(CorbaClientRequestDispatcherImpl.java:192) at com.sun.corba.ee.impl.protocol.CorbaClientDelegateImpl.request(CorbaClientDelegateImpl.java:184) at com.sun.corba.ee.impl.protocol.CorbaClientDelegateImpl.is_a(CorbaClientDelegateImpl.java:328) at org.omg.CORBA.portable.ObjectImpl._is_a(ObjectImpl.java:112) at org.omg.CosNaming.NamingContextHelper.narrow(NamingContextHelper.java:69) at com.sun.enterprise.naming.SerialContext.narrowProvider(SerialContext.java:134) at com.sun.enterprise.naming.SerialContext.getCachedProvider(SerialContext.java:259) at com.sun.enterprise.naming.SerialContext.getRemoteProvider(SerialContext.java:204) at com.sun.enterprise.naming.SerialContext.getProvider(SerialContext.java:159) at com.sun.enterprise.naming.SerialContext.lookup(SerialContext.java:409) at javax.naming.InitialContext.lookup(InitialContext.java:392) at com.werkii.latex.generator.Generator.main(Generator.java:344) Caused by: java.lang.RuntimeException: java.net.ConnectException: Connection refused: connect at com.sun.enterprise.iiop.IIOPSSLSocketFactory.createSocket(IIOPSSLSocketFactory.java:347) at com.sun.corba.ee.impl.transport.SocketOrChannelConnectionImpl.(SocketOrChannelConnectionImpl.java:244) ... 14 more Caused by: java.net.ConnectException: Connection refused: connect at sun.nio.ch.Net.connect(Native Method) at sun.nio.ch.SocketChannelImpl.connect(SocketChannelImpl.java:532) at com.sun.corba.ee.impl.orbutil.ORBUtility.openSocketChannel(ORBUtility.java:105) at com.sun.enterprise.iiop.IIOPSSLSocketFactory.createSocket(IIOPSSLSocketFactory.java:332) ... 15 more It's o.k. for now (while I'm still in development) that it bombs, but it does this repeatedly and the catch clause is never reached (even though I'm catching Throwable) - the message is not printed. So how can I handle connection errors during lookup in my program?

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  • Resuming execution of code after exception is thrown and caught

    - by dotnetdev
    Hi, How is it possible to resume code execution after an exception is thrown? For exampel, take the following code: namespace ConsoleApplication1 { class Test { public void s() { throw new NotSupportedException(); string @class = "" ; Console.WriteLine(@class); Console.ReadLine(); } } class Program { static void Main(string[] args) { try { new Test().s(); } catch (ArgumentException x) { } catch (Exception ex) { } } } } After catching the exception when stepping through, the program will stop running. How can I still carry on execution? Thanks

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  • System.Web.HttpException in asp.net mvc 2 on images and javascript files

    - by Rippo
    Hi I am getting the following errors reported by ELMAH on my asp.net mvc 2 site for javascript files, images etc. System.Web.HttpException: The remote host closed the connection I have done some research and it appears that the user/bot is clicking a link on the site before the page has fully loaded. Now this error never occurs on a controller action but always on a file that is on disk. e.g. /Content/CmsImages/logo.png /Content/CmsImages/MemberImages/Photo-001605.jpg /Content/jquery.tickertype.js So this means that all static files are being routed through the mvc pipeline. What options do I have?

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  • Assembly Programming and Interrupt Handling

    - by nmr
    I'm writing a program in assembly using MIPS architecture for a class, and I'm having trouble figuring out how to grab an input character by a user and store it in a register to process. The program would open a console, output a message, the user can then input a character and then this determines what is supposed to happen next in the program. Like I said, I'm having trouble figuring out how to grab the character so that I can act upon it in the program. thanks

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  • Better way to ignore exception type: multiple catch block vs. type querying

    - by HuBeZa
    There are situations that we like to ignore a specific exception type (commonly ObjectDisposedException). It can be achieved with those two methods: try { // code that throws error here: } catch (SpecificException) { /*ignore this*/ } catch (Exception ex) { // Handle exception, write to log... } or try { // code that throws error here: } catch (Exception ex) { if (ex is SpecificException) { /*ignore this*/ } else { // Handle exception, write to log... } } What are the pros and cons of this two methods (regarding performance, readability, etc.)?

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  • I have an Errno 13 Permission denied with subprocess in python

    - by wDroter
    The line with the issue is ret=subprocess.call(shlex.split(cmd)) cmd = /usr/share/java -cp pig-hadoop-conf-Simpsons:lib/pig-0.8.1-cdh3u1-core.jar:lib/hadoop-core-0.20.2-cdh3u1.jar org.apache.pig.Main -param func=cat -param from =foo.txt -x mapreduce fsFunc.pig The error is. File "./run_pig.py", line 157, in process ret=subprocess.call(shlex.split(cmd)) File "/usr/lib/python2.7/subprocess.py", line 493, in call return Popen(*popenargs, **kwargs).wait() File "/usr/lib/python2.7/subprocess.py", line 679, in __init__ errread, errwrite) File "/usr/lib/python2.7/subprocess.py", line 1249, in _execute_child raise child_exception OSError: [Errno 13] Permission denied Let me know if any more info is needed. Any help is appreciated. Thanks.

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  • How do I indicate that a class doesn't support certain operators?

    - by romeovs
    I'm writing a class that represents an ordinal scale, but has no logical zero-point (eg time). This scale should permit addition and substraction (operator+, operator+=, ...) but not multiplication. Yet, I always felt it to be a good practice that when one overloads one operator of a certain group (in this case the math operators), one should also overload all the others that belong to that group. In this case that would mean I should need to overload the multiplication and division operators also, because if a user can use A+B he would probable expect to be able the other operators. Is there a method that I can use to throw an error for this at compiler time? The easiest method would be just no to overload the operators operator*, ... yet it would seem appropriate to add a bit more explaination than operator* is not know for class "time". Or is this something that I really should not care about (RTFM user)?

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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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  • systematizing error codes for a web app in php?

    - by user151841
    I'm working on a class-based php web app. I have some places where objects are interacting, and I have certain situations where I'm using error codes to communicate to the end user -- typically when form values are missing or invalid. These are situations where exceptions are unwarranted ( and I'm not sure I could avoid the situations with exceptions anyways). In one object, I have some 20 code numbers, each of which correspond to a user-facing message, and a admin/developer-facing message, so both parties know what's going on. Now that I've worked over the code several times, I find that it's difficult to quickly figure out what code numbers in the series I've already used, so I accidentally create conflicting code numbers. For instance, I just did that today with 12, 13, 14 and 15. How can I better organize this so I don't create conflicting error codes? Should I create one singleton class, errorCodes, that has a master list of all error codes for all classes, systematizing them across the whole web app? Or should each object have its own set of error codes, when appropriate, and I just keep a list in the commentary of the object, to use and update that as I go along?

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  • Error handling in C++, constructors vs. regular methods

    - by Dennis Ritchie
    I have a cheesesales.txt CSV file with all of my recent cheese sales. I want to create a class CheeseSales that can do things like these: CheeseSales sales("cheesesales.txt"); //has no default constructor cout << sales.totalSales() << endl; sales.outputPieChart("piechart.pdf"); The above code assumes that no failures will happen. In reality, failures will take place. In this case, two kinds of failures could occur: Failure in the constructor: The file may not exist, may not have read-permissions, contain invalid/unparsable data, etc. Failure in the regular method: The file may already exist, there may not be write access, too little sales data available to create a pie chart, etc. My question is simply: How would you design this code to handle failures? One idea: Return a bool from the regular method indicating failure. Not sure how to deal with the constructor. How would seasoned C++ coders do these kinds of things?

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  • handling the logout functionality on the iPhone

    - by Nanz
    This is the first iPhone application i am working on. To use the application, the user has to login to our server. I am done with that part. Now the problem i am facing is how to logout the user from the server, deallocate all the memory and start afresh without quitting the app. After the user logs out, i want the exact same things to happen as in applicationdidfinishlaunching method. But i dont know how to go about it. The app has a tab bar which is set up in mainWindow.xib.

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