Thread: copy constructor

  1. #1

    copy constructor

    I am having trouble understanding 2 things.

    1. the difference between a copy constructor and an operator=
    What the actual use of the copy constructor is. I think I get the

    2. do we actually call the operator= or is it called whenever it is

  2. #2
    geek SilentStrike's Avatar
    Join Date
    Aug 2001
    The copy constructor, like all constructors, is only called once in an object's lifetime. Even when you do something like this,

    type a = b; // looks like assignment, but isn't

    It's the same as

    type a(b); // it's actually a copy constructor call

    However, if you want to change the state of an object to another object AFTER it has been created, that is when you use the operator =.

    type a(2);  // type(int) constructor
    type c(a);  // type(const type&) [copy constructor]
    type b;     // type() [default constructor]
    b = a;       // operator = (type, type)
    All calls to the = operator are explicit, but not everything that looks like it's using the = operator actually does.
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  3. #3
    Registered User
    Join Date
    Mar 2002
    the copy constructor is also called when an object is passed-by-value to a function and when a function returns an object

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