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  • C# equivalent of typeof for fields

    - by rwallace
    With reflection, you can look up a class from a string at run time, but you can also say typeof(Foo) and get compile time type checking, auto completion etc. If what you want is a field not a class, you can look it up from a string at runtime, but if you want compile time type checking etc., is there anyway to say something like fieldof(Foo.Bar)? I know the name of both the class and the field in advance, and I want to be able to refer to the field at compile time rather than with a run-time string lookup.

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  • null reference problems with c#

    - by alex
    Hi: In one of my window form, I created an instance of a class to do some works in the background. I wanted to capture the debug messages in that class and displayed in the textbox in the window form. Here is what I did: class A //window form class { public void startBackGroundTask() { B backGroundTask = new B(this); } public void updateTextBox(string data) { if (data != null) { if (this.Textbox.InvokeRequired) { appendUIDelegate updateDelegate = new appendUIDelegate(updateUI); try { this.Invoke(updateDelegate, data); } catch (Exception e) { Console.WriteLine(e.Message); } } else { updateUI(data); } } } private void updateUI(string data) { if (this.Textbox.InvokeRequired) { this.Textbox.Invoke(new appendUIDelegate(this.updateUI), data); } else { //update the text box this.Textbox.AppendText(data); this.Textbox.AppendText(Environment.NewLine); } } private delegate void appendUIDelegate(string data); } class B // background task { A curUI; public b( A UI) { curUI = UI; } private void test() { //do some works here then log the debug message to UI. curUI.updateTextBox("message); } } I keep getting a null reference exception after this.Invoke(updateDelegate, data); is called. I know passing "this" as a parameter is strange. But I want to send the debug message to my window form. Please help. Thanks

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  • jquery 1.3 not(:first) problem in IE

    - by sunil-mand99
    Hi, i have 3 div tags of same class, <div class="redc"> <p>sdfs</p> </div> <div class="redc"> <p>sdfs</p> </div> <div class="redc"> <p>sdfs</p> </div> to select div other than first ,$(".redc:not(:first)") works fine in mozilla,but not in IE Please suggest any alternative for IE Note: vesion jquery 1.3

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  • Why does Java think my object is a variable?

    - by user2896898
    Ok so I'm trying to make a simple pong game. I have a paddle that follows the mouse and a ball that bounces around. I wrote a method collidesWith(Sprite s) inside of my Sprite class that checks if the ball collides with the paddle (this works and isn't the problem). I have two objects extending my sprite class, a ball and a paddle object. So inside of my ball class I'm trying to check if it collides with the paddle. So I've tried if(this.collidesWith(paddle) == true){ System.out.println("They touched"); } I've also tried ball.collidesWith(paddle) and other combinations but it always says the same thing about the paddle (and the ball when I use ball.collidesWith) "Cannot find symbol. Symbol: variable paddle(or ball). Location: class Ball" So if I'm reading this right, it thinks that the paddle (and ball) are variables and it's complaining because it can't find them. How can I make it understand I am passing in objects, not variables? For extra information, an earlier assignment had me make two boxes and for them to change colors when they were colliding. In that assignment I used very similar code to above with if(boxOne.collidesWith(boxTwo) == true){ System.out.println("yes"); } And in this code it worked just fine. The program knew that boxOne and boxTwo were child classes of my Sprite class. Anyone know why they wouldn't work the same?

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  • C++ Template Classes and Copy Construction

    - by themoondothshine
    Is there any way I can construct an new object from the given object if the template parameters of both objects are identical at run-time? For example: I have a template class with the declaration: template<typename _Type1, typename _Type2> class Object; Next, I have two instantiations of the template: template class Object<char, int>; template class Object<wchar_t, wint_t>; Now, I want to write a member function such as: template<typename _Type1, typename _Type2> Object<char, int> Object<_Type1, _Type2>::toCharObject() { if(__gnu_cxx::__are_same<_Type1, char>::__value) return *this; else { //Perform some kind of conversion and return an Object<char, int> } } I have tried a couple of techniques, such as using __gnu_cxx::__enable_if<__gnu_cxx::__are_same<_Type1, char>::__value, _Type1>::__type in a copy constructor for the Oject class, but I keep running into the error: error: conversion from ‘Object<wchar_t, wint_t>’ to non-scalar type ‘Object<char, int>’ requested Is there no way I can do this? Any help will be greatly appreciated!

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  • A loop (while/foreach) with "offset" wrapping and

    - by DarkGhostHunter
    After applying what wrapping objects using math operator, I just tought it will be over. But no. By far. <?php $faces= array( 1 => '<div class="block">happy</div>', 2 => '<div class="block">sad</div>', (sic) 21 => '<div class="block">angry</div>' ); $i = 1; foreach ($faces as $face) { echo $face; if ($i == 3) echo '<div class="block">This is and ad</div>'; if ($i % 3 == 0) { echo "<br />"; // or some other wrapping thing } $i++; } ?> In the code I have to put and ad after the second one, becoming by that the third object. And then wrap the three all in a <div class="row"> (a br after won't work out by design reasons). I thought I will going back to applying a switch, but if somebody put more elements in the array that the switch can properly wrap, the last two remaining elements are wrapped openly. Can i add the "ad" to the array in the third position? That would make things simplier, only leaving me with guessing how to wrap the first and the third, the fourth and the sixth, an so on.

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  • Calling a constructor to reinitialize variables doesn't seem to work?

    - by Matt
    I wanted to run 1,000 iterations of a program, so set a counter for 1000 in main. I needed to reinitialize various variables after each iteration, and since the class constructor had all the initializations already written out - I decided to call that after each iteration, with the result of each iteration being stored in a variable in main. However, when I called the constructor, it had no effect...it took me a while to figure out - but it didn't reinitialize anything! I created a function exactly like the constructor - so the object would have its own version. When I called that, it reinitialized everything as I expected. int main() { Class MyClass() int counter = 0; while ( counter < 1000 ) { stuff happens } Class(); // This is how I tried to call the constructor initially. // After doing some reading here, I tried: // Class::Class(); // - but that didn't work either /* Later I used... MyClass.function_like_my_constructor; // this worked perfectly */ } ...Could someone try to explain why what I did was wrong, or didn't work, or was silly or what have you? I mean - mentally, I just figured - crap, I can call this constructor and have all this stuff reinitialized. Are constructors (ideally) ONLY called when an object is created?

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  • AJAX Closures and targeting 'this'

    - by Nick Lowman
    In the code example below the success callback function logs 'input#04.update' four times rather than each individual input, which makes sense seeing how closures work but how would I go about targeting each individual input using this. <input type="text" name="" id="01" class="update"> <input type="text" name="" id="02" class="update"> <input type="text" name="" id="03" class="update"> <input type="text" name="" id="04" class="update"> function updateFields(){ $('input.update').each(function(){ $this = $(this); $.ajax({ data: 'id=' + this.id, success: function(resp){ console.log($this); $this.val(resp) } }); }); }

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  • Using Visual Studio to make non aspx code-behind pages

    - by rizzle
    I want to build my own "code behind" like pages so that i can have HTML in a HTML file and code in cs file but be able to have Intellesense for the tokens in the HTML file. (i know that's what the .NET page class does, but i want to have something much lighter) EG: in the .html file: <%@ Directive classname="HTMLSnippet" %> <html> <body> <div>[%message%] </body> </html> and in a .cs file public class MyClass : HTMLSnippet { public class MyClass () { snippet.message = "message goes here" } } So my question is how do make the HTMLSnippet class so that it's members are automatically created, and specifically show up in Intellesense as i add tokens to the .html file? I know that .net currently does it by creating the designer.cs file and basically builds a class with all the elements from the page as it goes, and that would work fine but how can i get visual studio to generate that before compiling so that it shows up in Intellesense. Thanks! Clarification I'm not using this as a handler yet, i want to use this to have HTML snippets with tokens be usable in code as an object with properties. so almost like a custom control. I think what i have to do is create a VS add-in that waits for me to type tokens into an .html file then it automatically creates a .cs file with members for each token.

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  • Objects with inheritance memory storage

    - by nikitas350
    Say that i have some classes like this example. class A { int k, m; public: A(int a, int b) { k = a; m = b; } }; class B { int k, m; public: B() { k = 2; m = 3; } }; class C : private A, private B { int k, m; public: C(int a, int b) : A(a, b) { k = b; m = a; } }; Now, in a class C object, are the variables stored in a specific way? I know what happens in a POD object, but this is not a POD object...

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  • Problem with generics

    - by jess
    I have this code in base class protected virtual bool HasAnyStuff<TObject>(TObject obj) where TObject:class { return false; } In child class I am overriding protected override bool HasAnyStuff<Customer>(Customer obj) { //some stuff if Customer.sth etc return false; } I am getting this error '''Type parameter declaration must be an identifier not a type''' What is it I am doing wrong here?

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  • What's the outcome if I use free with new or delete with malloc?

    - by skydoor
    It is a compiler error or runtime error? The code below can be compiled! class Base{ void g(); void h(); }; int main() { Base* p = new Base(); free(p); return 0; } However it can't be compiled with a virtual function if I declare the class Base like this class Base{ virtual void g(); void h(); }; The code below can be compiled all the time, no matter the function is virtual or not. class Base{ void g(); void h(); }; int main() { Base* p = (Base*)malloc(sizeof(Base)); delete p; return 0; }

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  • Problems With SWT on Mac

    - by Jav
    I've got a java project that uses an SWT UI and I'm having trouble deploying it on any Mac OS X computers. The program itself works perfectly on Windows when it is either run from within Eclipse or from a jar file. On Mac, the program also works fine in Eclipse, but when I try to run it from a jar file, I get the following error: 2010-04-30 13:33:04.564 java[17825:41b] *** _NSAutoreleaseNoPool(): Object 0x10b9b0 of class NSCFString autoreleased with no pool in place - just leaking Stack: (0x944acf4f 0x943b9432 0x678fb79 0x35a19b1 0x359ba7f) 2010-04-30 13:33:04.566 java[17825:41b] *** _NSAutoreleaseNoPool(): Object 0x115ef0 of class NSCFNumber autoreleased with no pool in place - just leaking Stack: (0x944acf4f 0x943b9432 0x678a0b0 0x35a19b1 0x359ba7f) 2010-04-30 13:33:04.567 java[17825:41b] *** _NSAutoreleaseNoPool(): Object 0x121000 of class NSCFString autoreleased with no pool in place - just leaking Stack: (0x944acf4f 0x943b9432 0x678fb79 0x35a19b1) 2010-04-30 13:33:04.581 java[17825:41b] *** _NSAutoreleaseNoPool(): Object 0x123720 of class NSPathStore2 autoreleased with no pool in place - just leaking Stack: (0x944acf4f 0x943ba637 0x943c238f 0x943c1e8e 0x943c694b 0x678992e 0x35a19b1) 2010-04-30 13:33:04.582 java[17825:41b] *** _NSAutoreleaseNoPool(): Object 0x12d660 of class NSPathStore2 autoreleased with no pool in place - just leaking Stack: (0x944acf4f 0x943ba637 0x943b9739 0x943c3eb2 0x943c6b22 0x678992e 0x35a19b1) ... ... ... The actual error is much larger, and continues until the program crashes. I know that I am using the correct swt.jar file and I have tried running the program with the -XstartOnFirstThread VM argument, but still have not had any luck. Does anybody have any ideas or any suggestions where I could start looking for a solution? Thanks.

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  • C++ compile time polymorphism doubt ?

    - by user313921
    Below program contains two show() functions in parent and child classes, but first show() function takes FLOAT argument and second show() function takes INT argument. .If I call show(10.1234) function by passing float argument, it should call class A's show(float a) function , but it calls class B's show(int b). #include<iostream> using namespace std; class A{ float a; public: void show(float a) { this->a = a; cout<<"\n A's show() function called : "<<this->a<<endl; } }; class B : public A{ int b; public: void show(int b) { this->b = b; cout<<"\n B's show() function called : "<<this->b<<endl; } }; int main() { float i=10.1234; B Bobject; Bobject.show((float) i); return 0; } Output: B's show() function called : 10 Expected output: A's show() function called : 10.1234 Why g++ compiler chosen wrong show() function i.e class B's show(int b) function ?

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  • Avoiding instanceof in Java

    - by Mark Lutton
    Having a chain of "instanceof" operations is considered a "code smell". The standard answer is "use polymorphism". How would I do it in this case? There are a number of subclasses of a base class; none of them are under my control. An analogous situation would be with the Java classes Integer, Double, BigDecimal etc. if (obj instanceof Integer) {NumberStuff.handle((Integer)obj);} else if (obj instanceof BigDecimal) {BigDecimalStuff.handle((BigDecimal)obj);} else if (obj instanceof Double) {DoubleStuff.handle((Double)obj);} I do have control over NumberStuff and so on. I don't want to use many lines of code where a few lines would do. (Sometimes I make a HashMap mapping Integer.class to an instance of IntegerStuff, BigDecimal.class to an instance of BigDecimalStuff etc. But today I want something simpler.) I'd like something as simple as this: public static handle(Integer num) { ... } public static handle(BigDecimal num) { ... } But Java just doesn't work that way. I'd like to use static methods when formatting. The things I'm formatting are composite, where a Thing1 can contain an array Thing2s and a Thing2 can contain an array of Thing1s. I had a problem when I implemented my formatters like this: class Thing1Formatter { private static Thing2Formatter thing2Formatter = new Thing2Formatter(); public format(Thing thing) { thing2Formatter.format(thing.innerThing2); } } class Thing2Formatter { private static Thing1Formatter thing1Formatter = new Thing1Formatter(); public format(Thing2 thing) { thing1Formatter.format(thing.innerThing1); } } Yes, I know the HashMap and a bit more code can fix that too. But the "instanceof" seems so readable and maintainable by comparison. Is there anything simple but not smelly?

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  • C++ Template Usage

    - by MalcomTucker
    If I have a template definition like the one below, can someone provide a code sample for how I would actually instantiate an instance of this with two of my own classes? template <class T1, class T2> class LookUpTable { public: LookUpTable(); void set(Tl x, T2* y); T2* get(Tl x); }; Thanks.

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  • How do I filter values in a Django form using ModelForm?

    - by malandro95
    I am trying to use the ModelForm to add my data. It is working well, except that the ForeignKey dropdown list is showing all values and I only want it to display the values that a pertinent for the logged in user. Here is my model for ExcludedDate, the record I want to add: class ExcludedDate(models.Model): date = models.DateTimeField() reason = models.CharField(max_length=50) user = models.ForeignKey(User) category = models.ForeignKey(Category) recurring = models.ForeignKey(RecurringExclusion) def __unicode__(self): return self.reason Here is the model for the category, which is the table containing the relationship that I'd like to limit by user: class Category(models.Model): name = models.CharField(max_length=50) user = models.ForeignKey(User, unique=False) def __unicode__(self): return self.name And finally, the form code: class ExcludedDateForm(ModelForm): class Meta: model = models.ExcludedDate exclude = ('user', 'recurring',) How do I get the form to display only the subset of categories where category.user equals the logged in user?

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  • (Strange) C++ linker error in constructor

    - by Microkernel
    I am trying to write a template class in C++ and getting this strange linker error and can't figureout the cause, please let me know whats wrong with this! Here is the error message I am getting in Visula C++ 2010. 1>------ Rebuild All started: Project: FlashEmulatorTemplates, Configuration: Debug Win32 ------ 1> main.cpp 1> emulator.cpp 1> Generating Code... 1>main.obj : error LNK2019: unresolved external symbol "public: __thiscall flash_emulator<char>::flash_emulator<char>(char const *,struct FLASH_PROPERTIES *)" (??0?$flash_emulator@D@@QAE@PBDPAUFLASH_PROPERTIES@@@Z) referenced in function _main 1>C:\Projects\FlashEmulator_templates\VS\FlashEmulatorTemplates\Debug\FlashEmulatorTemplates.exe : fatal error LNK1120: 1 unresolved externals ========== Rebuild All: 0 succeeded, 1 failed, 0 skipped ========== Error message in g++ main.cpp: In function âint main()â: main.cpp:8: warning: deprecated conversion from string constant to âchar*â /tmp/ccOJ8koe.o: In function `main': main.cpp:(.text+0x21): undefined reference to `flash_emulator<char>::flash_emulator(char*, FLASH_PROPERTIES*)' collect2: ld returned 1 exit status There are 2 .cpp files and 1 header file, and I have given them below. emulator.h #ifndef __EMULATOR_H__ #define __EMULATOR_H__ typedef struct { int property; }FLASH_PROPERTIES ; /* Flash emulation class */ template<class T> class flash_emulator { private: /* Private data */ int key; public: /* Constructor - Opens an existing flash by name flashName or creates one with given FLASH_PROPERTIES if it doesn't exist */ flash_emulator( const char *flashName, FLASH_PROPERTIES *properties ); /* Constructor - Opens an existing flash by name flashName or creates one with given properties given in configFIleName */ flash_emulator<T>( char *flashName, char *configFileName ); /* Destructor for the emulator */ ~flash_emulator(){ } }; #endif /* End of __EMULATOR_H__ */ emulator.cpp #include <Windows.h> #include "emulator.h" using namespace std; template<class T>flash_emulator<T>::flash_emulator( const char *flashName, FLASH_PROPERTIES *properties ) { return; } template<class T>flash_emulator<T>::flash_emulator(char *flashName, char *configFileName) { return; } main.cpp #include <Windows.h> #include "emulator.h" int main() { FLASH_PROPERTIES properties = {0}; flash_emulator<char> myEmulator("C:\newEMu.flash", &properties); return 0; }

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  • simple javascript form code

    - by Steven Chaney
    I have a simple question about running some JS in a form i am trying to make it so that if a user selects an option (entry_12) in a drop down list, that the next form fields are not required (entry_11 entry_13 entry_11) those are the IDs for the fields any thoughts? im not sure where to start on this i have searched all over google and cannot find an instance of this. im trying to make it so if a user selects 'check' out of this list <div class="ss-item ss-item-required ss-select"><div class="ss-form-entry"><label class="ss-q-title" for="entry_12">Card Type <span class="ss-required-asterisk">*</span></label> <label class="ss-q-help" for="entry_12"></label> <select name="entry.12.single" id="entry_12"><option value="Check">Check</option> <option value="Mastercard">Mastercard</option> <option value="Visa">Visa</option> <option value="Amex">Amex</option> <option value="Discover">Discover</option></select></div></div></div> that the next fields (cvc code, exp date, cc number) arent required as they are if they had chosen CC

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  • Styling related issue in IE8

    - by Ajith
    I am using a background image to display as a button. The button shows up well in all versions of firefox, chrome, opera etc. However, the image fails to render itself in IE8. Only the image is not being shown, some of the other class styling gets applied such as width, height etc. Even more confounding is that in another page(though a different class and style sheet), an image of similar proportions gets displayed in similar usage. The image format is JPG. I'm copy-pasting the valid style attributes for both cases as shown by firebug below. None of the below buttons are displayed. button classes are applied as class="cart-button login", class="cart-button update", class="cart-button checkout" and class="cart-button continue" and are inside some divs. .cart-button{ height: 28px; cursor: pointer; border: none; float: left; } .cart-button:hover{ background-position: 0 -28px; } .login{ width: 58px; background:url(/../../templates/animalcare/i/login.jpg)no-repeat; margin:0 0 20px 0; clear: both; } .update{ width: 63px; background:url(/../../templates/animalcare/i/update.jpg)no-repeat; margin:0 0 20px 15px; float: left; } .checkout{ width: 77px; background:url(/../../templates/animalcare/i/checkout.jpg)no-repeat; float:right; margin:0 25px 30px 10px; } .continue{ width: 132px; background:url(/../../templates/animalcare/i/continue.jpg)no-repeat; float:right; margin:0 0 30px 0px; } The below is the only image button that gets displayed. It is located inside a table. It is in a different style sheet - hence the path difference. .add-to-cart{ width:102px; height:28px; float:left; background:url(i/add_to_cart.jpg) no-repeat; cursor:pointer; border:none; margin:10px 0 5px 0; } .add-to-cart:hover{ background-position:0 -28px; }

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  • Does Java have "properties" that work the same way properties work in C# (see the body of my text)?

    - by tyrone302
    In C#, you can use properties to make a data field publicly accessible (allowing the user to directly access it), and yet retain the ability to perform data validation on those directly-accessed fields. Doese Java have something similar? For Instance, suppose there exists a C# class with the following implementation(see below): public class newInt{ public newInt(){...} public int x{ get{ return this.x } set{ this.x = isValid(value) } } } private static int isValid(int value){...} This definition in the class allows the user to "naturally" use the data field 'x' when retrieving values from it and assigning values to it. Below is how it would be used in main. public class Test{ public static void main(String[] args){ newInt a = new newInt(); a.x = 50; int b = a.x; } } The question is... can java do this as well? if so, what is it called?

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  • Divs: Equal Horizontal Spacing

    - by Vecta
    I'm creating a site that has a series of four images on the homepage used as navigation with a large image beneath. <div style="width: 696px"> <div class="imglink"></div> <div class="imglink"></div> <div class="imglink"></div> <div class="imglink"></div> </div> <div style="width:696px"> ... </div> The "imglink" divs are 160px wide. I would like the images in the top div to be horizontally spaced evenly inside the div, with the two outer divs flush with the edges of the image below. I've been trying out floats, margins, padding, etc for a couple hours now and can't figure it out. Thanks for your help!

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  • Cannot create an array of LinkedLists in Java...?

    - by kchau
    I'm working on a sparse matrix class that needs to use an array of LinkedLists to store the values of a matrix. Each element of the array (i.e. each LinkedList) represents a row of the matrix. And, each element in the LinkedLists represents a column and the stored value. In my class, I have a declaration of the array as: private LinkedList<IntegerNode>[] myMatrix; And, in my constructor for the SparseMatrix, I try to define: myMatrix = new LinkedList<IntegerNode>[numRows]; The error I end up getting is "Cannot create a generic array of LinkedList<IntegerNode>." So, I have two issues with this, 1) What am I doing wrong, and 2) Why is the type acceptable in the declaration for the array if it can't be created? Edit: IntegerNode is a class that I have created. And, all of my class files are packaged together.

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  • redefinition c++

    - by coubeatczech
    hi, how does header including in c++ work? I have the classes already implemented in .h file and when there is #include in two files, there's this error: files.h:14:7: error: redefinition of ‘class abstract_file’ files.h:14:20: error: previous definition of ‘class abstract_file’ multiple times for each class and enum. Can anyone explain this?

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