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copy constructors quick question
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So when two objects are declared say class shoe shoe1 and class shoe shoe_copy and then shoe1's variables are set, if the line of code: shoe_copy=shoe1; what would that be doing? After all what is the real data structure of the objects of class shoe?
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shoe_copy=shoe1; will call the assignment operator, not the copy constructor. The copy constructor is called for example when you pass an object to a function by value.
// copy constructor called (notice I pass by value, not by reference)
void f(Shoe s)
{
}
// copy constructor called (notice I pass by value, not by reference)
void f(Shoe s)
{
}
Last edited by minas1; Feb 8th, 2009 at 5:41 am.
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yes but what willl shoe_copy=shoe1 do?
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Originally Posted by CPPRULZ 
yes but what willl shoe_copy=shoe1 do?
Let me explain:
Shoe shoe1; // calls the constructor
Shoe shoe_copy(shoe1); // copy constructor
Shoe shoe_copy = shoe1; // copy constructor, even if it seems it's the assignment operator;
shoe_copy = shoe1; // assignment operator
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but the last example shoe_copy=shoe1; - does that set the adresses equal or what does it physically do to shoe_copy.
It will not modify and addresses but it will set all of the values of shoe_copy to the values of shoe1. It wont call a copy constructor. I have seen this called a "shallow copy" (here)
Last edited by death_oclock; Feb 8th, 2009 at 9:02 pm.
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Ohhhh... okay that is probably the most informative clear article I have read on the subject and I thank you for that excellent link.
So when p=q calls the copy constructor is this accessing a compiler-defined ovverloaded version of the = operator?
So when p=q calls the copy constructor is this accessing a compiler-defined ovverloaded version of the = operator?
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sorry that last post was badly stated as a question, what I meant was: When p=q calls an overloaded assignment operator and preforms a shallow copy is this done using the automatic copy constructor that is called when an object is initialized to another?
So if i explicitly defined a complex copy constructor and said p=q that used the assignment operator would it preform a complex copy?
So if i explicitly defined a complex copy constructor and said p=q that used the assignment operator would it preform a complex copy?
No, the copy constructor is used only when called explicitly or when an object is being initialized. You could, however, have the assignment operator call your copy constructor.
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Originally Posted by death_oclock
No, the copy constructor is used only when called explicitly or when an object is being initialized. You could, however, have the assignment operator call your copy constructor.
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Last edited by ArkM; Feb 9th, 2009 at 6:07 pm.
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