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• How do I change the class of an object to a subclass of its current class in C++?

  - by Jared P

  I have an array of pointers to a base class, so that I can make those pointers point to (different) subclasses of the base class, but still interact with them. (really only a couple of methods which I made virtual and overloaded) I'm wondering if I can avoid using the pointers, and instead just make an array of the base class, but have some way to set the class to the subclass of my choosing. I know there must be something there specifying the class, as it needs to use that to look up the function pointer for virtual methods. By the way, the subclasses all have the same ivars and layout. Note: the design is actually based on using a template argument instead of a variable, due to performance increases, so really the abstract base class is just the interface for the subclasses, which are all the same except for their compiled code. Thanks

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• How to control the state of the buttons to be in present based on an event happened in a Silverlight app?

  - by vladc77

  I am trying to avoid building two buttons when I really need one. In my Silverlight app scenarios, I have few grids with a different content and buttons that control the visibility of these grids. I need to be able to show a different visual for a button when its content grid is visible. I can control states such as MouseOver and Pressed and more with visual state manage. However, I am not sure how to achieve this functionality with. I also can place an image on top of the button and switch the visibility of both but it is not perfect for what I need. I am wondering if there is any way to achieve this behavior. Any ideas are highly appreciated!

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• dates when saving to mysql database

  - by Patrick

  in my php code I was asking the user to choose day, month and year from some dropdown fields where values where 1, 2, 3 etc instead of 01, 02, 03. these were then combined to form a string like "YYYY-MM-DD" for the insertion in a db (in a date field). Having missed the initial 0, I thought I was sending strings in the wrong format, eg "YYYY-M-D" or YYYY-MM-D", but then I've noticed they appear in the right format in the database anyway: even if I submitted YYYY-M-D, it appeared as YYYY-MM-DD. is this the normal behaviour of mysql? if so, can i just avoid worrying about changing the code in my application?

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• How to create a web framework in C# without ASP?

  - by Mark

  I've managed to get a C# asp page running under ubuntu/apache/mono, but I don't want to write my framework in these ASP pages, I want to use straight C# and then I'll use a templating language for my views. But I don't know where to begin? C# is a compiled language, so... how would I do this? Would I compile everything and then have apache hook into the (single) executable and pass in the the request URL? Could I request specific .cs pages and then have apache tell it to compile and then "display" it only if it's been updated? Can the "view" files be compiled individually to avoid having to recompile everything every time there's a change? Is there some "base" I can work from, or am I going to have to reinvent accessing GET and POST variables (by reading header info) and all sorts of other stuff we take for granted in languages like PHP?

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• returning values from function or method multiple times by only calling the class once

  - by Sokhrat Sikar

  I have a members.php file that shows my websites members. I echo members name by using foreach method. A method of Members class returns an array, then I use foreach loop in the members.php file to echo the members. I am trying to aovid writing php code in my members.php file. Is there a way to avoid using foreach inside members.php file? For example, is it possible to return value from a method couple of times? (by only calling the object once). Just like how we normally call the functions? This question doesn't make sense, but I am just trying to see if there is a away around this issue?

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• Perl array and hash manipulation using map

  - by somebody

  I have the following test code use Data::Dumper; my $hash = { foo => 'bar', os => 'linux' }; my @keys = qw (foo os); my $extra = 'test'; my @final_array = (map {$hash->{$_}} @keys,$extra); print Dumper \@final_array; The output is $VAR1 = [ 'bar', 'linux', undef ]; Shouldn't the elements be "bar, linux, test"? Why is the last element undefined and how do I insert an element into @final_array? I know I can use the push function but is there a way to insert it on the same line as using the map command? Basically the manipulated array is meant to be used in an SQL command in the actual script and I want to avoid using extra variables before that and instead do something like: $sql->execute(map {$hash->{$_}} @keys,$extra);

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• Fast, cross-platform timer?

  - by dsimcha

  I'm looking to improve the D garbage collector by adding some heuristics to avoid garbage collection runs that are unlikely to result in significant freeing. One heuristic I'd like to add is that GC should not be run more than once per X amount of time (maybe once per second or so). To do this I need a timer with the following properties: It must be able to grab the correct time with minimal overhead. Calling core.stdc.time takes an amount of time roughly equivalent to a small memory allocation, so it's not a good option. Ideally, should be cross-platform (both OS and CPU), for maintenance simplicity. Super high resolution isn't terribly important. If the times are accurate to maybe 1/4 of a second, that's good enough. Must work in a multithreaded/multi-CPU context. The x86 rdtsc instruction won't work.

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• When designing an event, is it a good idea to prevent listeners from being added twice?

  - by Matt

  I am creating an event-based API where a user can subscribe to an event by adding listener objects (as is common in Java or C#). When the event is raised, all subscribed listeners are invoked with the event information. I initially decided to prevent adding an event listener more than once. If a listener is added that already exists in the listener collection, it is not added again. However, after thinking about it some more, it doesn't seem that most event-based structures actually prevent this. Was my initial instinct wrong? I'm not sure which way to go here. I guess I thought that preventing addition of an existing listener would help to avoid a common programming error. Then again, it could also hide a bug that would lead to code being run multiple times when it shouldn't.

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• ASP.NET GridView - how to enable validation declaratively

  - by Joe

  It it possible to enable validation in an ASP.NET GridView purely declaratively? What I've tried: A GridView bound to an ObjectDataSource with SelectMethod and UpdateMethod defined The GridView contains some ReadOnly BoundField columns and a TemplateField whose EditTemplate contains a TextBox and a RegularExpressionValidator that only allows numeric input in the TextBox. The GridView also contains a CommandField with ShowEditButton=true and CausesValidation=true. If I click on Edit, enter an invalid value, then click on Save, there is a PostBack, and an exception is thrown in the server (Input string was not in a correct format). I can of course avoid this by adding validation code to the RowUpdating event handler on the server (see below), but is there any declarative way to force the validation to be done without adding this code? protected void MyGridView_RowUpdating(object sender, GridViewUpdateEventArgs e) { Page.Validate("MyValidationGroup"); if (!Page.IsValid) { e.Cancel = true; } }

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• Redirect to prevent dup submission...but then you loose existing data

  - by coffeeaddict

  Here's the scenario User is on your checkout.aspx page Somewhere in the process, when clicking the pay button, you redirect the user to an intermediate page (before the confirmation page) to do some other logic. That intermediate page performs whatever logic based on a querystring flag you sent with the redirect from the checkout page This intermediate page also serves as an error page. So if any logic in the intermediatePage.aspx.cs fails I'm setting a message to be displayed on this page to the user If I refresh, that querystring value is still in the url..hence when it hits my Page_Load again, then the server-side logic is called & run again and I don't want this to happen The avoid this behavior/problem, the logical next step is to do a redirect back to the same page if they refresh (not sure how you'd catch that) to get rid of that querystring But when you redirect back to the same page your error message is gone, lost in the redirect therefore you end up showing them the same page but all values for the error message are now gone I do not want to solve this with Javascript either. I am not sure the best way to handle this.

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• Best practices to test protected methods with PHPUnit

  - by GrGr

  Hello, I found the discussion on Do you test private method informative. I have decided, that in some classes, I want to have protected methods, but test them. Some of these methods are static and short. Because most of the public methods make use of them, I will probably be able to safely remove the tests later. But for starting with a TDD approach and avoid debugging, I really want to test them. I thought of the following: Method Object as adviced in an answer seems to be overkill for this. Start with public methods and when code coverage is given by higher level tests, turn them protected and remove the tests. Inherit a class with a testable interface making protected methods public Which is best practice? Is there anything else? It seems, that JUnit automatically changes protected methods to be public, but I did not have a deeper look at it. PHP does not allow this via reflection.

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• JFileChooser returns incorrect path in OS X (folders only mode)

  - by Virat Kadaru

  I have a problem in java swing where the user has to select a folder, so I am using the code below. JFileChooser fc = new JFileChooser(); fc.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY); if(fc.showDialog(singleton, SELECT) == JFileChooser.APPROVE_OPTION) { File folder = fc.getSelectedFile(); String path = folder.getPath() + File.separatorChar + MYAPPFOLDER; } Now there are 2 ways a user may select the folder Navigate to the folder and select the folder Navigate to the folder, go into the folder, and click select Both ways work fine on windows but on OS X, I get If I do 1 : path = Users/<username>/Desktop/MYAPPFOLDER If I do 2 : path = Users/<username>/Desktop/Desktop/MYAPPFOLDER How do I avoid this 2nd case? Thanks in advance.

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• "Automatic" class proxy in C++

  - by PierreBdR

  I need to allow the user to change members of two data structures of the same type at the same time. For example: struct Foo { int a, b; } Foo a1 = {1,2}, a2 = {3,4}; dual(a1,a2)->a = 5; // Now a1 = {5,2} and a2 = {5,2} I have a class that works and that change first a1 and then copy a1 into a2. This is fine as long as: the class copied is small the user doesn't mind about everything being copied, not only the part modified. Is there a way to obtain this behavior: dual(a1,a2)->a = 5; // Now a1 = {5,2} and a2 = {5,4} I am opened to alternative syntax, but they should stay simple, and I would like to avoid things like: set_members(a1, a2, &Foo::a, 5); members(a1, a2, &Foo::a) = 5; or anything involving specifying explictely &Foo::

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• How can you check if a file exists before including/importing it in JSP?

  - by codeninja

  Assuming that requestScope.importMe is expecting a path to a jsp file <c:choose> <c:when test="${!empty requestScope.importMe && fileExists(requestScope.importMe) }"> <c:import url="${requestScope.importMe}" /> ... How can I check if the file exists before trying to include it so that an error is not thrown? I'd like to avoid using inline Java. Something using one of the JSTL tags is the preferred approach.

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• Submit multiple forms as one

  - by Stephen Sarcsam Kamenar

  I have two forms on the page. To the user it looks like 1 form, and I actually wish it was one form. But the way I'm trying to reuse code and include things, I can't avoid two forms in the source code... trying to act as one. I don't want to do ajax submit, I want a normal post submit, my form handler has redirects in it. How can I submit both of these, and get values that make sense on the server side. something like $_POST['form1]['whatever'] $_POST['form2]['thing'] Maybe take all the inputs from form 2, rename all of them with a prefix, and append them to form 1? I can't find a non-messy way of doing this. I don't think I need code, just a plan. Least messy idea wins.

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• UITableViewController executes delate functions before network request finishes

  - by user1543132

  I'm having trouble trying to populate a UITableView with the results of a network request. It seems that my code is alright as it works perfectly when my network is speedy, however, when it's not, the function - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath- still executes, which results in a bad access error. I presume that this is because the array that the aforesaid function attempts to utilize has not been populated. This brings me to my question: Is there anyway that I can have the UITableView delegate methods delayed to avoid this? - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"AlbumsCell"; //UITableViewCell *basicCell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath]; AlbumsCell *cell = (AlbumsCell *)[tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (!cell) { **// Here is where the Thread 1: EXC_BAD_ACCESS (code=2 address=0x8)** cell = [[[AlbumsCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } Album *album = [_albums objectAtIndex:[indexPath row]]; [cell setAlbum:album]; return cell; }

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• Do I have to hash twice in C#?

  - by Joe H

  I have code like the following: class MyClass { string Name; int NewInfo; } List<MyClass> newInfo = .... // initialize list with some values Dictionary<string, int> myDict = .... // initialize dictionary with some values foreach(var item in newInfo) { if(myDict.ContainsKey(item.Name)) // 'A' I hash the first time here myDict[item.Name] += item.NewInfo // 'B' I hash the second (and third?) time here else myDict.Add(item.Name, item.NewInfo); } Is there any way to avoid doing two lookups in the Dictionary -- the first time to see if contains an entry, and the second time to update the value? There may even be two hash lookups on line 'B' -- one to get the int value and another to update it.

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• div Height: 0 problem in IE

  - by meo

  to clear: both my content i use this: CSS: .clr { clear: both; height: 0; /* i have tried 0.001em to */ line-height: .001em; overflow: hidden; } HTML: <div class="clr">&nbsp;</div> it works perfectly in every navigator. But in IE 7 & 8 the div still have a height of a few pixels. How can i avoid this?

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• SWIG interface file questions

  - by morpheous

  I am writing a C/C++ extension module for other languages and I am using SWIG to generate the bindings. I have two questions Can I include more than 1 header file in the declaration part of the interface file e.g.: /* Declarations exposed to wrapper: */ > %{ > #define SWIG_FILE_WITH_INIT > #include "a.h" > #include "b.h" > #include "c.h" %} In all of the examples I have seen so far, after the header include declaration (as shown above), the functions declared in the header are then declared again in the interface file. Is this really necessary, as it means there are two copies of the function declarations that need to be maintained. Note: I can appreciate that some functions/methods declaration may need to be 'decorated' with the 'newobject' declaration so these obviously need to be in the interface file, to avoid memory leaks - however, I would have though that it would be sufficient to include the headers and then ONLY the declarations of the functions/methods that need to be declared with 'newobject' - is this recommended way of doing things?

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• HTML chrome:// page with select box, onChange failing

  - by Noitidart

  I have a html page. It is chrome://. I have a select box. Giving it the oncommand attribute won't work. So I have to use onchange however you have the typical problem with onchange where it doesnt work if user uses the keyboard arrows, or letters of items to change things. Is there anyway to attach onCommand to my select box? I want to avoid to use onkeyup as then i have to to validation to see if it really changed (which would require me saving previous values).

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• is vim able to detect in which language a file is written, and then load the correct dictionnary ?

  - by Niels

  I am using several languages, and by now I am obliged to indicate vim with which of these the spell check must be done. Is there a way to set up vim so that he automatically detects the correct one ? I remember vaguely that in a previous version of vim, when the spell check was not integrated, this was possible, using the vimspell script. It would be even better if this could apply not only to a file but also to a portion of a file, since I frequently mix several languages in a single file. Of course, I would like to avoid to load several dictionaries simultaneously.

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• Select n+1 problem

  - by Arnis L.

  Foo has Title. Bar references Foo. I have a collection with Bars. I need a collection with Foo.Title. If i have 10 bars in collection, i'll call db 10 times. bars.Select(x=x.Foo.Title) At the moment this (using NHibernate Linq and i don't want to drop it) retrieves Bar collection. var q = from b in Session.Linq<Bar>() where ... select b; I read what Ayende says about this. Another related question. A bit of documentation. And another related blog post. Maybe this can help? What about this? Maybe MultiQuery is what i need? :/ But i still can't 'compile' this in proper solution. How to avoid select n+1?

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• How to define an array inside a function in C?

  - by Arunav Dev

  So in my source file I have the folowin function: void update(state* old_state, state* measurement, uint32_t size) { state new_state[size]; //some function using measurement and old_state and returning the result in newstate arm_fadd_32(measurement,old_state,newstate,size); // rest of the code } Now the compiler throws an error saying that error#28:expression must have a constant value. I think it's due to the fact that even though inside the method the size local variable is not changing the compiler is expecting a constant while defining the size. I have tried the following: int const a = size; and then tried to reinitialize it says constant value is not known. I did some research in internet and it appears that there is no easier way without using malloc, which I don't want to since I am using the code for some embedded application. Is there a way to avoid this problem without really using malloc? Thanks in advance guys!

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• How can I lock the cursor to the inside of a window on Linux?

  - by ZorbaTHut

  I'm trying to put together a game for Linux which involves a lot of fast action and flinging around of the mouse cursor. If the user wants to play in windowed mode, I'd quite like to lock the cursor to the inside of the window to avoid accidentally changing programs in the heat of battle (obviously this will cancel itself if the user changes programs or hits escape for the pause menu.) On Windows, this can be accomplished easily with ClipCursor(). I can't find an equivalent on Linux. Is there one? I plan to do this in pure X code, but obviously if anyone knows of a way to do this in any Linux windowing library then I can just read the source code and figure out how to duplicate it in X.

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• How can I load an MP3 or similar music file for display and anaysis in wxWdigets?

  - by Jon Cage

  I'm developing a GUI in wxPython which allows a user to generate sequences of colours for some toys I'm building. Part of the program needs to load an MP3 (and potentially other formats further down the line) and display it to the user. That shuold be sufficient to get started but later I'd like to add features like identifying beats and some crude frequency analysis. Is there any simple way of loading / understanding an MP3's contents to display a plot of it's amplitudes to the screen using wxWidgets? I later intend to port to C++/wxWidgets for speed and to avoid having to distribute wxPython.

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