C/C++ :: Why Overloaded Copy Constructor Is Not Getting Called Here
Nov 19, 2012
#include<iostream>
using namespace std;
class Cents {
public:
int m_nCents;
Cents(int nCents=0):m_nCents(nCents){
cout<<"Calling normal constructor with value:"; m_nCents = nCents;
cout<<m_nCents<<endl;
[code].....
Question is :Why is the overloaded copy constructor that I have written not getting called here?Internally default copy constructor is getting called.Thats why we get value of obj2.m_nCents as 37.
The following are the cases when copy constructor is called.
1)When instantiating one object and initializing it with values from another object. 2)When passing an object by value. 3)When an object is returned from a function by value.
I don't understand #2 How can and object be passed by value? when I think of passing object I think of passing by address or reference. explain
I don't understand #3 how can a function returned object by value I think of again passing by address or reference.
I was wondering that why in the below code, the copy constructor is called 2 times.
Code: class A { private: static int count; int age; public: A()
[code].....
I think that when f(a) is called, since I am passing this as value, no copy constructor should be called. The copy constructor should called when the return object "x" is assigned to:
I have the following classes and 'dreaded diamond':
A / / B C / / D | | E
Classes B & C both inherit from A using public virtual A.
E is the only concrete class. None of the classes are totally abstract.
Every class has a copy constructor.
All of the copy constructors are chained together through the initialization lists.
E correctly calls D's copy constructor.
D correctly calls B and C's copy constructors.
But neither B nor C call A's copy constructor, although A's default constructor is called. To reiterate B and C have a call to A's copy constructor in their initialization lists.
I guess A's default constructor is being called is because of virtual inheritence, but why isn't its copy constructor called (too)?
A's copy constructor includes some very important code and I could do with calling it. Should I call it from the concrete class' initialization list or is that considered bad form?
The copy constructor is called twice, once when you pass an object by value, and once when the object is returned from a function by value. But why is the destructor being called twice?
I have two possible questions; can you use a ternary operator to initialize objects with overloaded constructors like
class thing { int x; int y;
[Code].....
I can get around it if I need to but I'd like to learn more about the ternary operator if I can, since I couldn't find anything online that addressed this particular issue, at least in a way I could detect.
When the below is done, does it call the constroctor only, and if yes, constructors do not have return types so how does it work? is there anything behind the scene?
wxAddHandler(new wxPNG_HANDLER); and sf::RenderWindow(sf::VideoMode(...),...);
I can't get my 'Front End' view model's constructor to be called. If i remove my dependency from the mvvm-light framework and use MSDN mvvm paterns then the constructor is called. What am i doing wrong. It seem like there is a data context binding issue between my XMAL and my view model backing.
ViewModelLocator.cs using GalaSoft.MvvmLight.Ioc; using Microsoft.Practices.ServiceLocation; using Point_Of_Sale.Model; using System.Collections.Generic; namespace Point_Of_Sale.ViewModel { public class ViewModelLocator
I am confused for first call to push_back copy constructor is called for second call I am expecting it to move class instance to new memory location there by trigering move and then inserting second class instance expected call:
Copy constructor Move constructor Copy constructor but its calling Copy constructor Copy constructor Move constructor
Exercise 7.24: Give your Screen class three constructors: a defaultconstructor; a constructor that takes values for height and width and initializes the contents to hold the given number of blanks; and a constructor that takes values for height, width, and a character to use as the contents of the screen.
Giving the screen a default constructor was easy. The next part is probably easy aswell, I just dont understand what they mean when they say "and initalize the contents to hold the given number of blanks" and something in the 3rd part when they say "character to use as the contents of the screen".
Think I have made a breakthrough... Would the constructor for the second part look like this:
copy constructor. I'm not really understanding them. I have a base class called Vehicle and a derived class called Car.
class Vehicle { private: int age;
[Code].....
I'm trying to test the new attributes and behavior of car but I think its not working because of the copy constructor. Its just not clicking. I also forgot that race car status is supposed to return yes or no, am I defining that right?
I can't find why it won't output the correct info for the array. I've looked until I am ready to throw the computer out the door. I'm at my wits end trying to get this to work right. I finally got it to quit killing the compiler, but it's doing this. The problem is in the insertBefore or insertAfter function calls and I don't think that my copy constructor is right.
How do i write main test program to test the copy constructor and assignment operator in this program...how do i know if its working as its suppose to?i just want to know about copy and assignment operator..i have figured out the test program for other things..Here my program :
I've been working on some project and I got to wondering when you know you need to use a copy constructor and an assignment operator. Is there a rule of thumb? I know there is the Rule of Three, but is there something that tells you when you need those three?
I have problems to put a list inside a linked list. I have the following conditions to fulfill:
- main.cpp can NOT be changed - There must be an abstract base class 'shape' - Methods such as area() and print() must be in code - Constructors is as follow:
Point( double x, double y, double size) Circle( double x, double y, double radie) Rectangle( double x, double y, double width, double height) Polygon( double x, double y, Vertex *varr, int num)
List::List(const List& list) { if ( list.empty() )
[Code].....
I think I'm not really able to track the new node for this reason my app crashes.
ListNode* p = list._pFront ; this is for the original node p ->_data;
the data inside the original node. Each node has three pointers. One for the entire node which tracks whether the node in front or in the back. The other two for next and previous nodes.
I know everything works except my copy constructor! There are no errors. The program crashes when it goes to access the copy constructor. why the copy constructor isn't working?
#ifdef _MSC_VER #define _CRT_SECURE_NO_WARNINGS #endif #include <cstring> // access to C str functions #include "String.h" // access String class using namespace std; String::String( int size )// default constructor
I'm working on a project and I'm not quite sure how to implement the Copy constructor and Overloaded assignment operator.
This is what the instructions say if that matters at all: Since you have dynamic variables in your class, you should make sure that the big three are implements. You already have the destructor, but you will need to add a copy constructor and the overloaded assignment operator. This is simpler than it sounds, but it requires some thinking. You need to make sure that both the copy constructor and the assignment operator create new containers.
