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• Set request attributes when a Form is POSTed

  - by ssahmed555

  Is there any way to set request attributes (not parameters) when a form is posted? The problem I am trying to solve is: I have a JSP page displaying some data in a couple of dropdown lists. When the form is posted, my Controller servlet processes this request (based on the parameters set/specified in the form) and redirects to the same JSP page that is supposed to display addition details. I now want to display the same/earlier data in the dropdown lists without having to recompute or recalculate to get that same data. And in the said JSP page, the dropdown lists in the form are populated by data that is specified through request attributes. Right now, after the Form is POSTed and I am redirected to the same JSP page the dropdown lists are empty because the necessary request attributes are not present. I am quite the n00b when it comes to web apps, so an obvious & easy solution to this problem escapes me at the moment! I am open to suggestions on how to restructure the control flow in the Servlet. Some details about this app: standard Servlet + JSP, JSTL, running in Apache Tomcat 6.0. Thanks.

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• Passing C++ object to C++ code through Python?

  - by cornail

  Hi all, I have written some physics simulation code in C++ and parsing the input text files is a bottleneck of it. As one of the input parameters, the user has to specify a math function which will be evaluated many times at run-time. The C++ code has some pre-defined function classes for this (they are actually quite complex on the math side) and some limited parsing capability but I am not satisfied with this construction at all. What I need is that both the algorithm and the function evaluation remain speedy, so it is advantageous to keep them both as compiled code (and preferrably, the math functions as C++ function objects). However I thought of glueing the whole simulation together with Python: the user could specify the input parameters in a Python script, while also implementing storage, visualization of the results (matplotlib) and GUI, too, in Python. I know that most of the time, exposing C++ classes can be done, e.g. with SWIG but I still have a question concerning the parsing of the user defined math function in Python: Is it possible to somehow to construct a C++ function object in Python and pass it to the C++ algorithm? E.g. when I call f = WrappedCPPGaussianFunctionClass(sigma=0.5) WrappedCPPAlgorithm(f) in Python, it would return a pointer to a C++ object which would then be passed to a C++ routine requiring such a pointer, or something similar... (don't ask me about memory management in this case, though :S) The point is that no callback should be made to Python code in the algorithm. Later I would like to extend this example to also do some simple expression parsing on the Python side, such as sum or product of functions, and return some compound, parse-tree like C++ object but let's stay at the basics for now. Sorry for the long post and thx for the suggestions in advance.

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• dojo.parser.parse only working first time it's called.

  - by crazymerlin

  I have a page that when a user clicks on a link for some reporting tools, it first asks them to enter some report parameters. I get the parameters dialog as a form using AJAX, based on the id of the link. Each dialog has some dojo controls on it, so I need to parse them when the dialog appears, because it is not originally part of the page. The first dialog when called works fine, but subsequent calls to dialogs fails to parse the dojo controls. Example: showParametersDialog : function(doc) { var content = doc.firstChild.firstChild.data; var container = document.createElement('div'); container.id = 'dialog'; container.innerHTML = content; container.style.background = 'transparent'; container.style.position = 'absolute'; container.style.top = (document.body.clientHeight / 2) - 124 + "px"; container.style.left = (document.body.clientWidth / 2) - 133 + "px"; container.style.display = 'block'; document.body.appendChild(container); // set up date fields var date_from = dojo.byId('date_from'); var date_to = dojo.byId('date_to'); try { date_from.value = dojo.date.locale.format(new Date(), {selector: 'date'}); date_to.value = dojo.date.locale.format(new Date(), {selector: 'date'}); } catch(e) { var now = new Date(); date_from.value = String(now.getMonth() + "/" + now.getDate() + "/" + now.getFullYear()); date_to.value = String(now.getMonth() + "/" + now.getDate() + "/" + now.getFullYear()); } dojo.parser.parse(); } All dialogs have the common date fields. So when I call this dialog the first time, and dojo.parser.parse() is called, it parses the controls on the dialog, but only the first time...after than, no dojo. Any thoughts? Thanks, Paul.

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• T4MVC Optional Parameter Inferred From Current Context

  - by Itakou

  I have read the other post about this at T4MVC OptionalParameter values implied from current context and I am using the latest T4MVC (2.11.1) which is suppose to have the fix in. I even checked checked to make sure that it's there -- and it is. I am still getting the optional parameters filled in based on the current context. For example: Let's say I have a list that is by default ordered by a person's last name. I have the option to order by first name instead with the URL http://localhost/list/stuff?orderby=firstname When I am in that page, I want to go back to order by first name with the code: @Html.ActionLink("order by last name", MVC.List.Stuff(null)) the link I wanted was simply http://localhost/list/stuff without any parameters to keep the URL simple and short - invoking default behaviors within the action. But instead the orderby is kept and the url is still http://localhost/list/stuff?orderby=firstname Any help would be great. I know that in the most general cases, this does remove the query parameter - maybe I do have a specific case where it was not removed. I find that it only happens when I have the URL inside a page that I included with RenderPartial. My actual code is <li>@Html.ActionLink("Recently Updated", MVC.Network.Ticket.List(Model.UI.AccountId, "LastModifiedDate", null, null, null, null, null))</li> <li>@Html.ActionLink("Recently Created", MVC.Network.Ticket.List(Model.UI.AccountId, "CreatedDate", null, null, null, null, null))</li> <li>@Html.ActionLink("Most Severe", MVC.Network.Ticket.List(Model.UI.AccountId, "MostSevere", null, null, null, null, null))</li> <li>@Html.ActionLink("Previously Closed", MVC.Network.Ticket.List(Model.UI.AccountId, "LastModifiedDate", null, "Closed", null, null, null))</li> the problem happens when someone clicks Previously Closed and and go to ?status=closed. When they click Recently Updated, which I want to the ?status so that it shows the active ones, the ?status=closed stays. Any insight would be greatly appreciated.

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• How to cancel a deeply nested process

  - by Mystere Man

  I have a class that is a "manager" sort of class. One of it's functions is to signal that the long running process of the class should shut down. It does this by setting a boolean called "IsStopping" in class. public class Foo { bool isStoping void DoWork() { while (!isStopping) { // do work... } } } Now, DoWork() was a gigantic function, and I decided to refactor it out and as part of the process broke some of it into other classes. The problem is, Some of these classes also have long running functions that need to check if isStopping is true. public class Foo { bool isStoping void DoWork() { while (!isStopping) { MoreWork mw = new MoreWork() mw.DoMoreWork() // possibly long running // do work... } } } What are my options here? I have considered passing isStopping by reference, which I don't really like because it requires there to be an outside object. I would prefer to make the additional classes as stand alone and dependancy free as possible. I have also considered making isStopping a property, and then then having it call an event that the inner classes could be subscribed to, but this seems overly complex. Another option was to create a "Process Cancelation Token" class, similar to what .net 4 Tasks use, then that token be passed to those classes. How have you handled this situation? EDIT: Also consider that MoreWork might have a EvenMoreWork object that it instantiates and calls a potentially long running method on... and so on. I guess what i'm looking for is a way to be able to signal an arbitrary number of objects down a call tree to tell them to stop what they're doing and clean up and return.

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• jQuery class selector oddness

  - by x3sphere

  I'm using jQuery to change the background image of a button depending on the class associated with it on hover. It only works if I put the hover statements in separate functions, however. Why is this? Here's the NON working code, always evaluates to the .submit hover statement, even when that class is removed via the keyup event. $(function() { { $('.submit-getinfo').hover(function () { $(this).css( {backgroundPosition: "right bottom"} ); }, function() { $(this).css( {backgroundPosition: "right top"} ); //$(this).removeClass('submithover'); }); $('.submit').hover(function () { $(this).css( {backgroundPosition: "left bottom"} ); }, function() { $(this).css( {backgroundPosition: "left top"} ); //$(this).removeClass('submithover'); }); }}); Working code: $(function() { { $('.submit').hover(function () { $(this).css( {backgroundPosition: "left bottom"} ); }, function() { $(this).css( {backgroundPosition: "left top"} ); //$(this).removeClass('submithover'); }); }}); $('#test').bind('keyup', function() { if (url == 'devel') { $("#submit").addClass("submit-getinfo").removeClass("submit"); $('.submit-getinfo').hover(function () { $(this).css( {backgroundPosition: "right bottom"} ); }, function() { $(this).css( {backgroundPosition: "right top"} ); //$(this).removeClass('submithover'); }); } } ); I just fail to see why I have to put the hover statements in separate functions, instead of sticking both in the main DOM.

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• Who needs singletons?

  - by sexyprout

  Imagine you access your MySQL database via PDO. You got some functions, and in these functions, you need to access the database. The first thing I thought of is global, like: $db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'root', 'pwd'); function some_function() { global $db; $db->query('...'); } But it's considered as a bad practice. So, after a little search, I ended up with the Singleton pattern, which "applies to situations in which there needs to be a single instance of a class." According to the example of the manual, we should do this: class Database { private static $instance, $db; private function __construct(){} static function singleton() { if(!isset(self::$instance)) self::$instance = new __CLASS__; return self:$instance; } function get() { if(!isset(self::$db)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd') return self::$db; } } function some_function() { $db = Database::singleton(); $db->get()->query('...'); } some_function(); But I just can't understand why you need that big class when you can do it merely with: class Database { private static $db; private function __construct(){} static function get() { if(!isset(self::$rand)) self::$db = new PDO('mysql:host=127.0.0.1;dbname=toto', 'user', 'pwd'); return self::$db; } } function some_function() { Database::get()->query('...'); } some_function(); This last one works perfectly and I don't need to worry about $db anymore. But maybe I'm forgetting something. So, who's wrong, who's right?

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• Will C++0x support __stdcall or extern "C" capture-nothing lambdas?

  - by Daniel Trebbien

  Yesterday I was thinking about whether it would be possible to use the convenience of C++0x lambda functions to write callbacks for Windows API functions. For example, what if I wanted to use a lambda as an EnumChildProc with EnumChildWindows? Something like: EnumChildWindows(hTrayWnd, CALLBACK [](HWND hWnd, LPARAM lParam) { // ... return static_cast<BOOL>(TRUE); // continue enumerating }, reinterpret_cast<LPARAM>(&myData)); Another use would be to write extern "C" callbacks for C routines. E.g.: my_class *pRes = static_cast<my_class*>(bsearch(&key, myClassObjectsArr, myClassObjectsArr_size, sizeof(my_class), extern "C" [](const void *pV1, const void *pV2) { const my_class& o1 = *static_cast<const my_class*>(pV1); const my_class& o2 = *static_cast<const my_class*>(pV2); int res; // ... return res; })); Is this possible? I can understand that lambdas that capture variables will never be compatible with C, but it at least seems possible to me that capture-nothing lambdas can be compatible.

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• Templates, Function Pointers and C++0x

  - by user328543

  One of my personal experiments to understand some of the C++0x features: I'm trying to pass a function pointer to a template function to execute. Eventually the execution is supposed to happen in a different thread. But with all the different types of functions, I can't get the templates to work. #include `<functional`> int foo(void) {return 2;} class bar { public: int operator() (void) {return 4;}; int something(int a) {return a;}; }; template <class C> int func(C&& c) { //typedef typename std::result_of< C() >::type result_type; typedef typename std::conditional< std::is_pointer< C >::value, std::result_of< C() >::type, std::conditional< std::is_object< C >::value, std::result_of< typename C::operator() >::type, void> >::type result_type; result_type result = c(); return result; } int main(int argc, char* argv[]) { // call with a function pointer func(foo); // call with a member function bar b; func(b); // call with a bind expression func(std::bind(&bar::something, b, 42)); // call with a lambda expression func( [](void)->int {return 12;} ); return 0; } The result_of template alone doesn't seem to be able to find the operator() in class bar and the clunky conditional I created doesn't compile. Any ideas? Will I have additional problems with const functions?

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• Why are argument substitutions not replaced during rescanning?

  - by James McNellis

  Consider the following macro definitions and invocation: #define x x[0] #define y(arg) arg y(x) This invocation expands to x[0] (tested on Visual C++ 2010, g++ 4.1, mcpp 2.7.2, and Wave). Why? Specifically, why does it not expand to x[0][0]? During macro replacement, A parameter in the replacement list...is replaced by the corresponding argument after all macros contained therein have been expanded. Before being substituted, each argument’s preprocessing tokens are completely macro replaced (C++03 §16.3.1/1). Evaluating the macro invocation, we take the following steps: The function-like macro y is invoked with x as the argument for its arg parameter The x in the argument is macro-replaced to become x[0] The arg in the replacement list is replaced by the macro-replaced value of the argument, x[0] The replacement list after substitution of all the parameters is x[0]. After all parameters in the replacement list have been substituted, the resulting preprocessing token sequence is rescanned...for more macro names to replace (C++03 §16.3.4/1). If the name of the macro being replaced is found during this scan of the replacement list...it is not replaced. Further, if any nested replacements encounter the name of the macro being replaced, it is not replaced (C++03 §16.3.4/2). The replacement list x[0] is rescanned (note that the name of the macro being replaced is y): x is identified as an object-like macro invocation x is replaced by x[0] Replacement stops at this point because of the rule in §16.3.4/2 preventing recursion. The replacement list after rescanning is x[0][0]. I have clearly misinterpreted something since all of the preprocessors I've tested say I am wrong. In addition, this example is a piece of a larger example in the C++0x FCD (at §16.3.5/5) and it too says that the expected replacement is x[0]. Why is x not replaced during rescanning? C99 and C++0x effectively have the same wording as C++03 in the quoted sections.

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• PHP OO vs Procedure with AJAX

  - by vener

  I currently have a AJAX heavy(almost everything) intranet webapp for a business. It is highly modularized(components and modules ala Joomla), with plenty of folders and files. ~ 80-100 different viewing pages (each very unique in it's own sense) on last count and will likely to increase in the near future. I based around the design around commands and screens, the client request a command and sends the required data and receives the data that is displayed via javascript on the screen. That said, there are generally two types of files, a display files with html, javascript, and a little php for templating. And also a php backend file with a single switch statement with actions such as, save, update and delete and maybe other function. There is very little code reuse. Recently, I have been adding an server sided undo function that requires me to reuse some code. So, I took the chance to try out OOP but I notice that some functions are so simple, that creating a class, retrieving all the data then update all the related rows on the database seems like overkill for a simple action as speed is quite critical. Also I noticed there is only one class in an entire file. So, what if the entire php is a class. So, between creating a class and methods, and using global variables and functions. Which is faster?

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• Query Parameter Value Is Null When Enum Item 0 is Cast to Int32

  - by Timothy

  When I use the first item in a zero-based Enum cast to Int32 as a query parameter, the parameter value is null. I've worked around it by simply setting the first item to a value of 1, but I was wondering though what's really going on here? This one has me scratching my head. Why does the parameter regarded the value as null, instead of 0? Enum LogEventType : int { SignIn, SignInFailure, SignOut, ... } private static DataTable QueryEventLogSession(DateTime start, DateTime stop) { DataTable entries = new DataTable(); using (FbConnection conn = new FbConnection(DSN)) { using (FbDataAdapter adapter = new FbDataAdapter( "SELECT event_type, event_timestamp, event_details FROM event_log " + "WHERE event_timestamp BETWEEN @start AND @stop " + "AND event_type IN (@signIn, @signInFailure, @signOut) " + "ORDER BY event_timestamp ASC", conn)) { adapter.SelectCommand.Parameters.AddRange(new Object[] { new FbParameter("@start", start), new FbParameter("@stop", stop), new FbParameter("@signIn", (Int32)LogEventType.SignIn), new FbParameter("@signInFailure", (Int32)LogEventType.SignInFailure), new FbParameter("@signOut", (Int32)LogEventType.SignOut)}); Trace.WriteLine(adapter.SelectCommand.CommandText); foreach (FbParameter p in adapter.SelectCommand.Parameters) { Trace.WriteLine(p.Value.ToString()); } adapter.Fill(entries); } } return entries; }

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• Why is T() = T() allowed?

  - by Rimo

  I believe the expression T() creates an rvalue (by the Standard). However, the following code compiles (at least on gcc4.0): class T {}; int main() { T() = T(); } I know technically this is possible because member functions can be invoked on temporaries and the above is just invoking the operator= on the rvalue temporary created from the first T(). But conceptually this is like assigning a new value to an rvalue. Is there a good reason why this is allowed? Edit: The reason I find this odd is it's strictly forbidden on built-in types yet allowed on user-defined types. For example, int(2) = int(3) won't compile because that is an "invalid lvalue in assignment". So I guess the real question is, was this somewhat inconsistent behavior built into the language for a reason? Or is it there for some historical reason? (E.g it would be conceptually more sound to allow only const member functions to be invoked on rvalue expressions, but that cannot be done because that might break some existing code.)

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• Why null reference exception in SetMolePublicInstance?

  - by OldGrantonian

  I get a "null reference" exception in the following line: MoleRuntime.SetMolePublicInstance(stub, receiverType, objReceiver, name, null); The program builds and compiles correctly. There are no complaints about any of the parameters to the method. Here's the specification of SetMolePublicInstance, from the object browser: SetMolePublicInstance(System.Delegate _stub, System.Type receiverType, object _receiver, string name, params System.Type[] parameterTypes) Here are the parameter values for "Locals": + stub {Method = {System.String <StaticMethodUnitTestWithDeq>b__0()}} System.Func<string> + receiverType {Name = "OrigValue" FullName = "OrigValueP.OrigValue"} System.Type {System.RuntimeType} objReceiver {OrigValueP.OrigValue} object {OrigValueP.OrigValue} name "TestString" string parameterTypes null object[] I know that TestString() takes no parameters and returns string, so as a starter to try to get things working, I specified "null" for the final parameter to SetMolePublicInstance. As already mentioned, this compiles OK. Here's the stack trace: Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.ExtendedReflection.Collections.Indexable.ConvertAllToArray[TInput,TOutput](TInput[] array, Converter`2 converter) at Microsoft.Moles.Framework.Moles.MoleRuntime.SetMole(Delegate _stub, Type receiverType, Object _receiver, String name, MoleBindingFlags flags, Type[] parameterTypes) at Microsoft.Moles.Framework.Moles.MoleRuntime.SetMolePublicInstance(Delegate _stub, Type receiverType, Object _receiver, String name, Type[] parameterTypes) at DeqP.Deq.Replace[T](Func`1 stub, Type receiverType, Object objReceiver, String name) in C:\0VisProjects\DecP_04\DecP\DeqC.cs:line 38 at DeqPTest.DecCTest.StaticMethodUnitTestWithDeq() in C:\0VisProjects\DecP_04\DecPTest\DeqCTest.cs:line 28 at Starter.Start.Main(String[] args) in C:\0VisProjects\DecP_04\Starter\Starter.cs:line 14 Press any key to continue . . . To avoid the null parameter, I changed the final "null" to "parameterTypes" as in the following line: MoleRuntime.SetMolePublicInstance(stub, receiverType, objReceiver, name, parameterTypes); I then tried each of the following (before the line): int[] parameterTypes = null; // if this is null, I don't think the type will matter int[] parameterTypes = new int[0]; object[] parameterTypes = new object[0]; // this would allow for various parameter types All three attempts produce a red squiggly line under the entire line for SetMolePublicInstance Mouseover showed the following message: The best overloaded method match for 'Microsoft.Moles.Framework.Moles.MoleRuntime.SetMolePublicInstance(System.Delegate, System.Type, object, string, params System.Type[])' has some invalid arguments. I'm assuming that the first four arguments are OK, and that the problem is with the params array.

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• How do I handle freeing unmanaged structures on application close?

  - by LostKaleb

  I have a C# project in which i use several unmanaged C++ functions. More so, I also have static IntPtr that I use as parameters for those functions. I know that whenever I use them, I should implement IDisposable in that class and use a destructor to invoke the Dispose method, where I free the used IntPtr, as is said in the MSDN page. public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } private void Dispose(bool disposing) { // Check to see if Dispose has already been called. if (!this.disposed) { if (disposing) { component.Dispose(); } CloseHandle(m_InstanceHandle); m_InstanceHandle = IntPtr.Zero; disposed = true; } } [System.Runtime.InteropServices.DllImport("Kernel32")] private extern static Boolean CloseHandle(IntPtr handle); However, when I terminate the application, I'm still left with a hanging process in TaskManager. I believe that it must be related to the used of the MarshalAs instruction in my structures: [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct SipxAudioCodec { [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public string CodecName; public SipxAudioBandwidth Bandwidth; public int PayloadType; } When I create such a structure should I also be careful to free the space it allocs using a destructor? [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct SipxAudioCodec { [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public string CodecName; public SipxAudioBandwidth Bandwidth; public int PayloadType; ~SipxAudioCodec() { Marshal.FreeGlobal(something...); } }

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• Array's index and argc signedness

  - by tusbar

  Hello, The C standard (5.1.2.2.1 Program startup) says: The function called at program startup is named main. [...] It shall be de?ned with a return type of int and with no parameters: int main(void) { /* ... */ } or with two parameters [...] : int main(int argc, char *argv[]) { /* ... */ } And later says: The value of argc shall be nonnegative. Why shouldn't argc be defined as an unsigned int, argc supposedly meaning 'argument count'? Should argc be used as an index for argv? So I started wondering if the C standard says something about the type of array's index. Is it signed? 6.5.2.1 Array subscripting: One of the expressions shall have type ‘‘pointer to object type’’, the other expression shall have integer type, and the result has type ‘‘type’’. It doesn't say anything about its signedness (or I didn't find it). It is pretty common to see codes using negatives array indexes (array[-1]) but isn't it undefined behavior? Should array's indexes be unsigned?

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• How can one make a 'passthru' function in C++ using macros or metaprogramming?

  - by Ryan

  So I have a series of global functions, say: foo_f1(int a, int b, char *c); foo_f2(int a); foo_f3(char *a); I want to make a C++ wrapper around these, something like: MyFoo::f1(int a, int b, char* c); MyFoo::f2(int a); MyFoo::f3(char* a); There's about 40 functions like this, 35 of them I just want to pass through to the global function, the other 5 I want to do something different with. Ideally the implementation of MyFoo.cpp would be something like: PASSTHRU( f1, (int a, int b, char *c) ); PASSTHRU( f2, (int a) ); MyFoo::f3(char *a) { //do my own thing here } But I'm having trouble figuring out an elegant way to make the above PASSTHRU macro. What I really need is something like the mythical X getArgs() below: MyFoo::f1(int a, int b, char *c) { X args = getArgs(); args++; //skip past implicit this.. ::f1(args); //pass args to global function } But short of dropping into assembly I can't find a good implementation of getArgs().

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• Generating python wrapper for 3ed party c++ dll using swig with

  - by MuraliK

  I am new bee to swig. I have a third party c++ dll with the following functions export. I want to call these dll functions in python. So thought of using swig to generate the wrapper using swig. I am not sure what sort of wrapper i need to generate (do i need to generate .lib or .dll to use it in python?). In case i need to generate .dll how do i do that using visual studio 2010. There are some call back function like SetNotifyHandler(void (__stdcall * nf)(int wp, void *lp)) in the bellow list. How do define such function in interface file. can someone help me plese? enter code here #ifndef DLL_H #define DLL_H #ifdef DLL_BUILD #define DLLFUNC __declspec(dllexport) #else #define DLLFUNC __declspec(dllimport) #endif #pragma pack(push) #pragma pack(1) #pragma pack(pop) extern "C" { DLLFUNC int __stdcall StartServer(void); DLLFUNC int __stdcall GetConnectionInfo(int connIndex, Info *buf); DLLFUNC void __stdcall SetNotifyWindow(HWND nw); DLLFUNC void __stdcall SetNotifyHandler(void (__stdcall * nf)(int wp, void *lp)); DLLFUNC int __stdcall SendCommand(int connIndex, Command *cmd); };

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• Adding a column to a model at runtime (without additional tables) in rails

  - by Marek

  I'm trying to give admins of my web application the ability to add some new fields to a model. The model is called Artwork and i would like to add, for instante, a test_column column at runtime. I'm just teting, so i added a simple link to do it, it will be of course parametric. I managed to do it through migrations: def test_migration_create Artwork.add_column :test_column, :integer flash[:notice] = "Added Column test_column to artworks" redirect_to :action => 'index' end def test_migration_delete Artwork.remove_column :test_column flash[:notice] = "Removed column test_column from artworks" redirect_to :action => 'index' end It works, the column gets added/ removed to/from the databse without issues. I'm using active_scaffold at the moment, so i get the test_column field in the form without adding anything. When i submit a create or an update, however, the test_column does not get updated and stay empty. Inspecting the parameters, i can see: Parameters: {"commit"=>"Update", "authenticity_token"=>"37Bo5pT2jeoXtyY1HgkEdIhglhz8iQL0i3XAx7vu9H4=", "id"=>"62", "record"=>{"number"=>"test_artwork", "author"=>"", "title"=>"Opera di Test", "test_column"=>"TEEST", "year"=>"", "description"=>""}} the test_column parameter is passed correctly. So why active record keeps ignoring it? I tried to restart the server too without success. I'm using ruby 1.8.7, rails 2.3.5, and mongrel with an sqlite3 database. Thanks

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• Why won't Internet Explorer (or Chrome) display my 'Loading...' gif but Firefox will?

  - by codeLes

  I have a page that fires several xmlHttp requests (synchronous, plain-vanilla javascript, I'd love to be using jquery thanks for mentioning that). I'm hiding/showing a div with a loading image based on starting/stopping the related javascript functions (at times I have a series of 3 xmlhttp request spawning functions nested). div = document.getElementById("loadingdiv"); if(div) { if(stillLoading) { div.style.visibility='visible'; div.style.display=''; } else { div.style.visibility='hidden'; div.style.display='none'; } } In Firefox this seems to work fine. The div displays and shows the gif for the required processing. In IE/Chrome however I get no such feedback. I am only able to prove that the div/image will even display by putting alert() methods in place with I call the above code, this stops the process and seems to give the browsers in question the window they need to render the dom change. I want IE/Chrome to work like it works in Firefox. What gives?

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• How to prevent VC++ 9 linker from linking unnecessary global variables?

  - by sharptooth

  I'm playing with function-level linking in VC++. I've enabled /OPT:REF and /OPT:ICF and the linker is happy to eliminate all unused functions. Not so with variables. The following code is to demonstrate the problem only, I fully understand that actually having code structured that way is suboptimal. //A.cpp SomeType variable1; //B.cpp extern SomeType variable1; SomeType variable2; class ClassInB { //actually uses variable1 }; //C.cpp extern SomeType variable2; class ClassInC { //actually uses variable2; }; All those files are compiled into a static lib. The consumer project only uses ClassInC and links to the static library. Now comes the VC++ 9 linker. First the linker sees that C.obj references variable2 and includes B.obj. B.obj references variable1, so it includes A.obj. Then the unreferenced stuff elimination phase starts. It removes all functions in A.obj and B.obj, but not the variables. Both variable and variable2 are preserved together with their static initializers and deinitializers. That inflates the image size and introduces a delay for running the initializers and deinitializes. The code above is oversimplified, in actual code I really can't move variable2 into C.cpp easily. I could put it into a separate .cpp file, but that looks really dumb. Is there any better option to resolve the problem with Visual C++ 9?

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• LINQ to SQL: NOTing a prebuilt expression

  - by ck

  I'm building a library of functions for one of my core L2S classes, all of which return a bool to allow checking for certain situations. Example: Expression<Func<Account, bool>> IsSomethingX = a => a.AccountSupplementary != null && a.AccountSupplementary.SomethingXFlag != null && a.AccountSupplementary.SomethingXFlag.Value; Now to query where this is not true, I CAN'T do this: var myAccounts= context.Accounts .Where(!IsSomethingX); // does not compile However, using the syntax from the PredicateBuilder class, I've come up with this: public static IQueryable<T> WhereNot<T>(this IQueryable<T> items, Expression<Func<T, bool>> expr1) { var invokedExpr = Expression.Invoke(expr1, expr1.Parameters.Cast<Expression>()); return items.Where(Expression.Lambda<Func<T, bool>> (Expression.Not(invokedExpr), expr1.Parameters)); } var myAccounts= context.Accounts .WhereNot(IsSomethingX); // does compile which actually produces the correct SQL. Does this look like a good solution, and is there anything I need to be aware of that might cause me problems in future?

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• Performing measures within the execution of a c++ code every t milliseconds

  - by user506901

  Given a while loop and the function ordering as follows: int k=0; int total=100; while(k<total){ doSomething(); if(approx. t milliseconds elapsed) { measure(); } ++k; } I want to perform 'measure' every t-th milliseconds. However, since 'doSomething' can be close to the t-th millisecond from the last execution, it is acceptable to perform the measure after approximately t milliseconds elapsed from the last measure. My question is: how could this be achieved? One solution would be to set timer to zero, and measure it after every 'doSomething'. When it is withing the acceptable range, I perform measures, and reset. However, I'm not which c++ function I should use for such a task. As I can see, there are certain functions, but the debate on which one is the most appropriate is outside of my understanding. Note that some of the functions actually take into account the time taken by some other processes, but I want my timer to only measure the time of the execution of my c++ code (I hope that is clear). Another thing is the resolution of the measurements, as pointed out below. Suppose the medium option of those suggested.

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• Is it advisable to have an interface as the return type?

  - by wb

  I have a set of classes with the same functions but with different logic. However, each class function can return a number of objects. It is safe to set the return type as the interface? Each class (all using the same interface) is doing this with different business logic. protected IMessage validateReturnType; <-- This is in an abstract class public bool IsValid() <-- This is in an abstract class { return (validateReturnType.GetType() == typeof(Success)); } public IMessage Validate() { if (name.Length < 5) { validateReturnType = new Error("Name must be 5 characters or greater."); } else { validateReturnType = new Success("Name is valid."); } return validateReturnType; } Are there any pitfalls with unit testing the return type of an function? Also, is it considered bad design to have functions needing to be run in order for them to succeed? In this example, Validate() would have to be run before IsValid() or else IsValid() would always return false. Thank you.

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• TDD approach for complex function

  - by jamie

  I have a method in a class for which they are a few different outcomes (based upon event responses etc). But this is a single atomic function which is to used by other applications. I have broken down the main blocks of the functionality that comprise this function into different functions and successfully taken a Test Driven Development approach to the functionality of each of these elements. These elements however aren't exposed for other applications would use. And so my question is how can/should i easily approach a TDD style solution to verifying that the single method that should be called does function correctly without a lot of duplication in testing or lots of setup required for each test? I have considered / looked at moving the blocks of functionality into a different class and use Mocking to simulate the responses of the functions used but it doesn't feel right and the individual methods need to write to variables within the main class (it felt really heath robinson). The code roughly looks like this (i have removed a lot of parameters to make things clearer along with a fair bit of irrelevant code). public void MethodToTest(string parameter) { IResponse x = null; if (function1(parameter)) { if (!function2(parameter,out x)) { function3(parameter, out x); } } // ... // more bits of code here // ... if (x != null) { x.Success(); } }

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