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  • Is there a way to cause a new C++ class instance to fail, if certain conditions in the contructor ar

    - by Jim Fell
    As I understand it, when a new class is instantiated in C++, a pointer to the new class is returned, or NULL, if there is insufficient memory. I am writing a class that initializes a linked list in the constructor. If there is an error while initializing the list, I would like the class instantiator to return NULL. For example: MyClass * pRags = new MyClass; If the linked list in the MyClass constructor fails to initialize properly, I would like pRags to equal NULL. I know that I can use flags and additional checks to do this, but I would like to avoid that, if possible. Does anyone know of a way to do this? Thanks.

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  • C++ static classes & shared_ptr memory leaks

    - by HardCoder1986
    Hello! I can't understand why does the following code produce memory leaks (I am using boost::shared_ptr with static class instance). Could someone help me? #include <crtdbg.h> #include <boost/shared_ptr.hpp> using boost::shared_ptr; #define _CRTDBG_MAP_ALLOC #define NEW new(_NORMAL_BLOCK, __FILE__, __LINE__) static struct myclass { static shared_ptr<int> ptr; myclass() { ptr = shared_ptr<int>(NEW int); } } myclass_instance; shared_ptr<int> myclass::ptr; int main() { _CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF | _CRTDBG_CHECK_ALWAYS_DF | _CrtSetDbgFlag(_CRTDBG_REPORT_FLAG)); return 0; }

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  • java - find out the type of class which implements of other classes

    - by Johnzzz
    i have a kind of specific problem, let's say, that i have public interface A { } //------------------------------ public class B implements A{ static int countx = 0; } //---------------------------------- public class C implements A{ static int county = 0; } //---------------------------------- public class Arc { public A from; public A to; //======================================== and now I have an object a (which is an instance of Arc) and I want to find out whether it is an instance of B or C and get to the atributes countX or countY (stg like a.from.countX) any ideas? :)

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  • C++ Typing and OOP child classes

    - by Zack
    I'm a bit confused: If I have a base class A, and a class B which extends A, can a variable of the type A hold a value of the type B and vice versa? If yes, why? Aren't they completely different even if B is derived from A? How about type-safety? If this is possible, what things do I have to mind when taking use of this? How would this work out in terms of performance? Note: Sorry if I asked too many questions, just ignore them and just look out for those "marked" with the list decoration dot :) Also, this is not my homework. I'm a hobby programmer and have skills in scripting languages with OOP, yet I'm relatively new to OOP typing in C++.

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  • How do I write a writer method for a class variable in Ruby?

    - by tepidsam
    I'm studying Ruby and my brain just froze. In the following code, how would I write the class writer method for 'self.total_people'? I'm trying to 'count' the number of instances of the class 'Person'. class Person attr_accessor :name, :age @@nationalities = ['French', 'American', 'Colombian', 'Japanese', 'Russian', 'Peruvian'] @@current_people = [] @@total_people = 0 def self.nationalities #reader @@nationalities end def self.nationalities=(array=[]) #writer @@nationalities = array end def self.current_people #reader @@current_people end def self.total_people #reader @@total_people end def self.total_people #writer #-----????? end def self.create_with_attributes(name, age) person = self.new(name) person.age = age person.name = name return person end def initialize(name="Bob", age=0) @name = name @age = age puts "A new person has been instantiated." @@total_people =+ 1 @@current_people << self end

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  • Problem with accessing classes from another class.

    - by srikanth rongali
    I have a classA, classB,classC. I have another class classABC; All are CCLayer inherited. I need to call all the classA, classB, classC from classABC. #import <Foundation/Foundation.h> #import "cocos2d.h" @interface classABC : CCLayer { classA *aClass; } @property(nonatomic, retain)classA *aClass; @end #import "classABC" #import "classA.h" #import "classB.h" #import "classC.h" @implementation classABC -(id)init { if( (self = [super init]) ) { ClassA *aClass = [[ClassA alloc]init]; CCScene *aClassS = [CCScene node]; CCLayer * aClassL = [aClass node]; [aClassS addChild: aClassL]; [[CCDirector sharedDirector] setAnimationInterval:60.0/60]; [[CCDirector sharedDirector] replaceScene: aClass]; } return self; } @end But I am not getting the classA displayed. How should I do it ? Thank You.

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  • Compiling C++ when two classes references one another

    - by Omry
    I am trying to write a simple wrapper around a connection pointer that will return it to the pool when the wrapper is destroyed. but it wont compile because the ConnectionPool and AutoConn need each other to be declared. I tried to use forward deceleration but it didn't work. how do I solve this? (using g++) class Connection {}; class ConnectionPool { Connection *m_c; public: AutoConn getConn() { return AutoConn(this, m_c); // by value } void releaseConnection(Connection *c) { } }; class AutoConn { ConnectionPool* m_pool; Connection *m_connection; public: AutoConn(ConnectionPool* pool, Connection *c) : m_pool(pool), m_connection(c) {} ~AutoConn() { m_pool->releaseConnection(m_connection); } };

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  • Change update value of property (LINQTOSQL)

    - by Dynde
    Hi... I've got an entity object - Customer, with a property called VATRate. This VATRate is in the form of a decimal (0.25). I wanted to be able to enter a percentage value, and save it in the correct decimal value in the database, so I made this custom property: partial class Customer{ public decimal VatPercent { get{ ... //Get code works fine} set { this.VATRate = (value / 100); } } } And then I just bind this property instead of VATRate in my ASPX editTemplate (formview). This actually works - at least one time, when I debug an update, the value is set correctly one time, and then right after it gets set to the old value. I can't really see why it sets the value twice (and with the old value the second time). Can anyone shed some light on this?

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  • Custom Control in ASP.NET C#

    - by Gal V
    Hello all, I created a simple custom control that only inherits from the Literal control, and doesn't have any extensions yet, code is empty. Namespace: CustomControls Class name: Literal : System.Web.UI.WebControls.Literal Next thing I do is registering this control in the aspx page as following: <%@ Register TagPrefix="web" Namespace="CustomControls" % (I read in few tutorials that this is one of the ways to register it, besides web.config etc.) After all, no intellisence for me, and worse- I get a parse error 'unknown server tag: web' when I try to run the page with the control in it. I used 'create new project' and not new website, in case this info is needed. What could be my problem? Thanks in advance.

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  • Java GC: top object classes promoted (by size)?

    - by Java Geek
    Hello! Please let me know what is the best way to determine composition of young generation memory promoted to old generation, after each young GC event? Ideally I would like to know class names which are responsible say, for 80% of heap in each "young gen - old gen" promotion chunk; Example: I have 600M young gen, each tenure promotes 6M; I want to know which objects compose this 6M. Thank you.

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  • classes in obj.c

    - by palominoz
    @interface MainViewController : UIViewController < FlipsideViewControllerDelegate { } I am quite new to object oriented languages & especially obj.c. I need to use addressbook framework within this class.Apple documentation suggests this code: @interface ViewController : UIViewController < ABPeoplePickerNavigationControllerDelegate {} I was wondering how to use at the same time FlipSideControllerDelegate & ABPeoplePickerControllerDelegate. In fact I really can't understand what i am doing:)

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  • Accessing variablss through a different class within the constructor of latter classes of an object

    - by Haxed
    In the code below, I've added two lines that print output. The first line prints junk as usual, but surprisingly the second one gives me a compilation error. Why? class Student { private String name; public Student(String name){ this.name = name; } public String getName(){ return name; } } class StudentServer { public StudentServer(){ Student[] s = new Student[30]; s[0] = new Student("Nick"); // LINE 01: This compiles, although prints junk System.out.println(s[0]); // LINE 02: I get a error called cannot find symbol System.out.println(s[0].getName()); } public static void main(){ new StudentServer(); } } Many Thanks

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  • What's the benefit of declaring class functions separately from their actual functionality?

    - by vette982
    In C++, what's the benefit of having a class with functions... say class someClass{ public: void someFunc(int arg1); }; then having the function's actual functionality declared after int main int main() { return 0; } void someClass::someFunc(int arg1) { cout<<arg1; } Furthermore, what's the benefit of declaring the class in a .h header file, then putting the functionality in a .cpp file that #includes the .h file?

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  • Nested Dynamic PHP Class

    - by user338844
    Alright, I may just need a terminology update, but I have been playing in Magento and Joomla, and they do references like $mage = new Mage; $mage->block('blockname'); where class Mage through some process I am failing to figure out is calling: class blockname extends something{ } Don't quote me on that code, however I am looking to do something like that where I have a file that I can do $myscript-block('blockname'); and it will load and call the file with class blockname. I hope that is not too confusing, but any help is appreciated. Thanks in advance!

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  • Using a part of a class in multiple projects

    - by Axarydax
    I have a set of methods that do some utility work over SQL connection, and until now these have been copied over from project to project. But as time goes on, project numbers have grown and I need to keep these methods in sync in case I find a bug or need to update it. I have managed to get it to the state that SQL access class is a partial class, one part is specific for project and contains wrappers for a specific database. The second part is the common one and contains methods that are used in all project-specific databases. The problem is that now I would have the "utility" class copied over 8 projects, with the same content, but in different namespaces. In C/C++ it would have been simple, because I would just have #included the contents of the file wherever needed. What should I do in C#?

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  • Javascript methods, classes and events

    - by Randy Gurment
    Hi, how should I document this piece of code: // Is this class? colors = { // Is this method? "red" : function() { // Do something... } // Still method? "black" : { // So what is this? "black-1" : function() { /* Do something */ } } } I am using YUI Doc. These tags are available @module @class @method @event @property

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  • Why does coffeescript generate classes like this?

    - by ryeguy
    Given the following coffeescript code: class Animal constructor: (@name) -> speak: (things) -> "My name is #{@name} and I like #{things}" This is generated: var Animal = (function() { function Animal(name) { this.name = name; } Animal.prototype.speak = function(things) { return "My name is " + this.name + " and I like " + things; }; return Animal; })(); But why isn't this more idiomatic code generated? var Animal = function Animal(name) { this.name = name; }; Animal.prototype.speak = function(things) { return "My name is " + this.name + " and I like " + things; }; I know that coffeescript wraps a lot of stuff in anonymous functions to control scope leak, but what could leak here?

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  • Confusion over C++ new operator and classes

    - by Nils
    Hi all I created a simple class in C++ which has a private dynamic array. In the constructor I initialize the array using new and in the destructor I free it using delete. When I instantiate the class using Class a = Class(..); it works as expected, however it seems I cannot instantiate it using the new operator (Like Class *a = new Class(..);), I always get a segmentation fault. What I don't understand is when I should use new to instantiate a class and when just call the constructor or should it be possible to instantiate a class either with new or by just calling the constructor. float** A = new float*[3]; for (int i=0; i<3; i++) { A[i] = new float[3]; } A[0][0] = 3; A[0][1] = 3; A[0][2] = 4; A[1][0] = 5; A[1][1] = 6; A[1][2] = 7; A[2][0] = 1; A[2][1] = 2; A[2][2] = 3; Matrix *M = new Matrix(A, 3, 3); delete[] A; delete M; Below the class definition.. class Matrix { private: int width; int height; int stride; float* elements; public: Matrix(float** a, int n, int m); ~Matrix(); }; Matrix::Matrix(float** a, int n, int m) { // n: num rows // m: elem per rows elements = new float[n*m]; for (int i=0; i<n; i++) { for (int j=0; j<m; j++) { elements[i*n + j] = a[n][m]; } } } Matrix::~Matrix() { delete[] elements; }

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  • jquery switch element classes

    - by Sobakinet
    Please take a look here: http://jsfiddle.net/ZUd27/7/ What I need: There are several elements. One of them is active and visible. If I hover over any inactive element, it becomes visible and active. The previously active element becomes inactive. On mouseout, nothing happens - the last hovered element stays active. My problems: The first active element always stays active (in DOM?). It becomes invisible, but on next mouseover nothing happens. Other elements don't behave as they should. If one of them is active, on next mousein it becomes invisible. thx

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  • printing the instance in Python

    - by kame
    Hello! With this code: class Complex: def __init__(self, realpart, imagpart): self.real = realpart self.imag = imagpart print self.real, self.imag class Circle: def __init__(self, radius): print "A circle wiht the radius", radius, "has the properties:" print "circumference =", 3.14*radius print "area =", 3.14*radius**2 I get this output: >>> Complex(3,2) 3 2 <__main__.Complex instance at 0x01412210> But why does he print the last line?

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  • Dynamic proxies to auto-save models

    - by atomman
    I'm trying to make some auto-magic happen in java using proxies to track objects and saving them when a set* method is called. I started of using java's built in Proxy, and everything works just fine, but from what I can understand I need a interface for every model, which is something that I'm trying to avoid. This is where CGLIB comes in, it allows me to create proxies of my models without the use of interfaces. BUT, how can I now retrieve the original object, the one I am trying to save? The optimal solution to be would be something like the EntityManager interface used by hibernate, where you keep your original object, but it is still tracked.

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