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  • Accessing initialized variable on different class C++

    - by d0pe
    I'm having some difficulties with this problem. The main idea is, I initialized a variable of class type B in class A, class A.h has the variable Z declared as public, like B *Z; In class A.cpp, I initialized it as Z = new B(); Now, I want to access that variable from class C and I'm unable to do so. C.h includes A.h and B.h

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  • C++: What is the size of an object of an empty class?

    - by Ashwin
    I was wondering what could be the size of an object of an empty class. It surely could not be 0 bytes since it should be possible to reference and point to it like any other object. But, how big is such an object? I used this small program: #include <iostream> using namespace std; class Empty {}; int main() { Empty e; cerr << sizeof(e) << endl; return 0; } The output I got on both Visual C++ and Cygwin-g++ compilers was 1 byte! This was a little surprising to me since I was expecting it to be of the size of the machine word (32 bits or 4 bytes). Can anyone explain why the size of 1 byte? Why not 4 bytes? Is this dependent on compiler or the machine too? Also, can someone give a more cogent reason for why an empty class object will not be of size 0 bytes?

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  • jQuery Animation and Classes

    - by ehdv
    Assume you have a list item, <li id="foo"> which you want to fade from one color to another when moused over, and that you are using jQuery. This is fairly easy: $('li#foo').bind('mouseenter' , function(e) { $(this).animate({backgroundColor: '#F00'} , 300); }); However, what if you wanted to get the resulting color or other style rules from a class defined in CSS without also declaring them in JavaScript? It seems there's no way to learn style information from CSS rules without having an example of the rule already in the document, which would require you to animate the <li> to the target appearance, then in the animation-finished callback, set the class which leads to redundant style declarations and can foul up your CSS at "runtime". Sorry if this question's unclear: It doesn't occur in the context of any specific project, I'm just curious how you'd go about this. Also, I know CSS3 hypothetically includes support for such transitions but using CSS for dynamic behavior like this seems such an ugly hack.

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  • question regarding "this" pointer in c++

    - by sil3nt
    hello there, i have been given class with int variables x and y in private, and an operator overload function, class Bag{ private: int x; int y; public: Bag(); ~Bag(); //....... //.....etc }; Bag operator+ (Bag new) const{ Bag result(*this); //what does this mean? result.x += new.x; result.y += new.y; } What is the effect of having "Bag result(*this);" there?.

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  • C++: Initialization Order for Member Classes

    - by Nikhil
    In the following code, when the ctor of X is called will the ctor of A or B be called first? Does the order in which they are placed in the body of the class control this? If somebody can provide a snippet of text from the C++ standard that talks about this issue, that would be perfect. class A; class B; class X { private: A a; B b; }

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  • Same function on multiple div classes doesn't work

    - by Sebass van Boxel
    I'm doing something terribly wrong and just can't find the solution for it. Situation: I've got a number of products with a number of quotes per product. Those quote automatically scroll in a div. If the scroll reaches the last quote is scroll back to the first one. What works: The function basically works when it's applied on 1 div, but when applied on multiple div it doesn't scroll back to the first one or keeps scrolling endlessly. This is the function i've written for this: function quoteSlide(divname){ $total = ($(divname+" > div").size()) $width = $total * 160; $(divname).css('width', ($width)); console.log ($totalleft *-1); if ($width - 160 > $totalleft *-1){ $currentleft = $(divname).css('left'); $step = -160; $totalleft = parseInt($currentleft)+$step; }else{ $totalleft = 0; } $(divname).animate(     { left: $totalleft }, // what we are animating     'slow', // how fast we are animating     'swing', // the type of easing     function() { // the callback }); } It's being executed by something like: quoteSlide('#quotecontainer_1'); in combination with a setInterval so it keeps scrolling automatically. This is the jsFiddle where it goes wrong (So applied on more than 1 div) http://jsfiddle.net/FsrbZ/. This is the jsFiddle where everything goes okay. (applied on 1 div) When changing the following: quoteSlide('#quotecontainer_1'); quoteSlide('#quotecontainer_2'); setInterval(function() { quoteSlide('#quotecontainer_1'); quoteSlide('#quotecontainer_2'); }, 3400);? to quoteSlide('#quotecontainer_1'); setInterval(function() { quoteSlide('#quotecontainer_1'); }, 3400);? it does work... but only on 1 quotecontainer.

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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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  • Car Class (first time with classes)

    - by user2967605
    For an assignment I needed to use a class named car and have it display the make and model, and also have the speed increase by 5 when you use accelerate and decrease by 5 when you brake. My teacher helped me along the way but when I got to the end I couldn't get it to run. Could someone correct me and tell my why it's wrong? Imp--------- #include <iostream> #include <string> using namespace std; void accelerate() { int speed; speed = speed + 5; } void brake() { int speed; speed = speed - 5; } Header #include <iostream> #include <string> using namespace std; class car { public: car(int getYear, string getMake); void accelerate(); void brake(); private: int year; string make; int speed; }; CarClass.cpp #include <string> #include "CarClass.h" using namespace std; int main() { car.(2013,"Kia") car.accelerate() car.brake() }

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  • C++ methods which take templated classes as argument.

    - by Nils
    I have a templated class Vector<class T, int N> Where T is the type of the components (double for example) and n the number of components (so N=3 for a 3D vector) Now I want to write a method like double findStepsize(Vector<double,2> v) {..} I want to do this also for three and higher dimensional vectors. Of course I could just introduce further methods for higher dimensions, but the methods would have a lot of redundant code, so I want a more generic solution. Is there a way to create a method which takes a templated class without further specializing it (in this case without specifying T or N)? Like double findStepsize(Vector<T,N> v) ?

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  • Criteria: search for two different entity classes...

    - by RoCMe
    Hi! I have a "super entity" SuperEntity and three entities ChildEntity1, ..., ChildEntity3 which extends the super class. It's easy to search for all entities in the database, i.e. we could use session.createCriteria(SuperEntity.class); It's no problem to search for one specific entity type, too, just replace the SuperEntity with any of the children to look for entities of that type. But I have a problem when allowing 'multiple choice' for the types. I.e., it could be neccessary to search all entities of type 1 and 2, but not of type 3. A first idea was to create two independent queries and join the results in a final list - but that would destroy the paging which uses offset and limit functionality of the database... Is there a possibility in Criteria to join two different queries in one single result list? Kind regards, RoCMe

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  • Pointer-like behavior in Java

    - by Shmoo
    I got the following: class A{ int foo; } class B extends A{ public void bar(); } I got a instance of A and want to convert it to an instance of B without losing the reference to the variable foo. For example: A a = new A(); a.foo = 2; B b = a; <-- what I want to do. //use b b.foo = 3; //a.foo should now be 3 Thanks for any help!

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  • C++ array of classes

    - by nickik
    I working on a game but I have a problem with the initialization of the level. (feld is just field in german) class level{ private: feld spielfeld[10][10]; public: /* other staff */ void init_feld(); }; void level::init_feld() { for(int i=0;i!=10;i++){ for(int n=0;n!=10;n++){ spielfeld[i][n] = new feld(land, i, n); } } } The Error: Error: no match for »operator=« in »((level*)this)-level::spielfeld[i][n] = (operator new(24u), (, ((feld*))))« /home/nick/stratego/feld.h:18:11: Remark: candidate is: feld& feld::operator=(const feld&) Process terminated with status 1 (0 minutes, 0 seconds) 2 errors, 0 warnings

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  • C# do nested classes need to be instantiated?

    - by JL
    In the following scenario: public class outerclass { public innerClass Ic {get;set} public class innerClass { } } Do you need to instantiate the inner class property before assigning values to it, like this? public class outerclass { public outerclass() { this.Ic = new innerClass(); } public innerClass Ic {get;set} public class innerClass { } }

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  • Accessing variables in other classes (Java)

    - by George
    Why doesn't the following program return 0, since I am accessing p from a new A(), which has not had main called on it? public class A { public int p = 0; public static void main(String[] args) { p = Integer.parseInt(args[0]); new B().go(); } } class B { public void go() { System.out.println(new A().p); } }

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  • Problem with C++ classes

    - by Mike
    I have a class defined called extBlock. I then make an instance of that class with this extBlock mainBlock = new extBlock(1, 1024); I get this error: error C2440: 'initializing' : cannot convert from 'extBlock *' to 'extBlock' Can anyone help me with why I am getting this error. I have seen examples online of declaring it like this with a pointer extBlock *mainBlock = new extBlock(1, 1024); But if I do it this way it does not let me call the functions of mainBlock

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  • Fading between two classes in jquery

    - by Andy
    I would like to be able to fadeout this class <h2 class="care-home-fees"><a title="Care Home Fees" href="#">Text</a></h2> and fade in this <h2 class="care-home-fees-over"><a title="Care Home Fees" href="#">Text</a></h2> Notice there are two separate images Here is my current markup which doesnt seem to work $(document).ready(function(){ $("h2.care-home-fees").hover( function () { $(this).addClass("care-home-fees-over"); }, function () { $(this).removeClass("care-home-fees"); } ); }); and the button printed before any change <h2 class="care-home-fees"><a title="Care Home Fees" href="#">Text</a></h2>

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  • JQuery validation using is() and multiple CSS classes

    - by Alex
    Hi Folks, Trying to debug something that basically .trim()'s, .val()'s and .length's a textarea input as HTML below (truncated): <form id="Kontaktanfrage" method="post" action="tests/testform/"> ... <textarea cols="50" rows="8" id="el_12" name="FORM[Kontaktanfrage][el_12]" title="Ihre Nachricht: *" class="textarea required"></textarea> ... </form> JavaScript: function validateField(formId, fieldId) { if (fieldId) { var element = "form#"+formId+" input#"+fieldId; var fieldValue = jQuery.trim(jQuery(element).val()); var fieldLength = fieldValue.length; var fieldError = ""; if ($(element).is('.textarea.required') && fieldLength == 0) { fieldError = "error message"; } } } The above if check is never true. Using JQuery: 1.4.1. Having seen other examples online, I can't see what the difference should be. Feel free to test it in FireBug at (http://www.initiat.de/tests/testform/). Any help appreciated, can't see what I'm doing wrong.

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  • Name hiding from inherited classes

    - by Mercerbearman
    I have the following sample code and I wanted to know the correct way to get access to the Pass method in the CBar class. Currently I have found 3 ways to get access to this method and they are as follows: Casting the object, ((CBar *) &foo)-Pass(1, 2, 3); Using this syntax, foo.CBar::Pass(1,2,3); Use the "using" syntax in the CFoo class declaration, using CBar::Pass. The following is an example of a simple project to test this capability. Foo.h #include "bar.h" class CFoo : public CBar { private: double m_a; double m_b; public: CFoo(void); ~CFoo(void); void Pass(double a, double b); }; Foo.cpp #include "Foo.h" CFoo::CFoo(void) { m_a = 0.0; m_b = 0.0; } CFoo::~CFoo(void) { } void CFoo::Pass(double a, double b) { m_a = a; m_b = b; } Bar.h class CBar { int m_x; int m_y; int m_z; public: CBar(void); ~CBar(void); void Pass(int x, int y, int z); }; Bar.cpp #include "Bar.h" CBar::CBar(void) { m_x = 0; m_y = 0; m_z = 0; } CBar::~CBar(void) { } void CBar::Pass(int x, int y, int z) { m_x = x; m_y = y; m_z = z; } And my main class DoStuff.cpp #include "DoStuff.h" #include "Foo.h" CDoStuff::CDoStuff(void) { } CDoStuff::~CDoStuff(void) { } int main() { CFoo foo, foo1, foo2; //This only gets to the Pass method in Foo. foo.Pass(2.5, 3.5); //Gets access to Pass method in Bar. foo1.CBar::Pass(5,10,15); //Can also case and access by location for the same result?? ((CBar *) &foo2)->Pass(100,200,300); return 0; } Are each of these options viable? Are some preferred? Are there pitfalls with using any one of the methods listed? I am especially curious about the foo.CBar::Pass(1,2,3) syntax. Thanks, B

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  • C++ classes use of double colon [duplicate]

    - by user2444217
    This question already has an answer here: What does the :: mean in C++? 5 answers What Does :: Mean? 3 answers I am learning C++. Now I don't fully understand what this does Some_Class::SomeClass { etc... } I would do some research for myself, but I'm not sure where to begin or what's it called. Help would be appreciated.

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  • Defining Proper Classes with Java

    - by user2579706
    Ok, I'm studying Java and have the following question: "Assume you defined a class named MyClass. A student wants to use your class and tries to declare an instance named myObj and instantiate it. He tried the following: MyObj MyClass = new MyClass( ); Why won't his code work? Show how he should correct it. " I'm not sure how to do this? Can anyone point me in the right direction? Many thanks.

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  • Why am I seeing so many instantiable classes without state?

    - by futlib
    I'm seeing a lot of instantiable classes in the C++ and Java world that don't have any state. I really can't figure out why people do that, they could just use a namespace with free functions in C++, or a class with a private constructor and only static methods in Java. The only benefit I can think of is that you don't have to change most of your code if you later decide that you want a different implementation in certain situations. But isn't that a case of premature design? It could be turned into a class later, when/if it becomes appropriate. Am I getting this wrong? Is it not OOP if I don't put everything into objects (i.e. instantiated classes)? Then why are there so many utility namespaces and classes in the standard libraries of C++ and Java? Update: I've certainly seen a lot examples of this in my previous jobs, but I'm struggling to find open source examples, so maybe it's not that common after all. Still, I'm wondering why people do it, and how common it is.

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