The copy constructor

[pocmatos]

Hi all,

Imagine I have:
class X {
public:
// Some methods...

private:
vector<MyObject*> vec;

};

I think that the default copy constructor will just copy an object of
this class into a new one where vec is new by the pointers inside vec
will point to the exact same place as the original one, right? It'll
not copy MyObject also, right?

If I want this I'll have to implement my own copy constructor... i.e.
I'll have to implement X(X&) and operator= on X, right?

This is just my intuition but I would appreciate some feedback, thanks.

Cheers,

Paulo Matos

 

[Ian Collins]

Hi all,

Imagine I have:
class X {
public:
// Some methods...

private:
vector<MyObject*> vec;

};

I think that the default copy constructor will just copy an object of
this class into a new one where vec is new by the pointers inside vec
will point to the exact same place as the original one, right? It'll
not copy MyObject also, right?

If I want this I'll have to implement my own copy constructor... i.e.
I'll have to implement X(X&) and operator= on X, right?

right.

 

[Rolf Magnus]

Hi all,

Imagine I have:
class X {
public:
// Some methods...

private:
vector<MyObject*> vec;

};

I think that the default copy constructor will just copy an object of
this class into a new one where vec is new by the pointers inside vec
will point to the exact same place as the original one, right? It'll not
copy MyObject also, right?

Yes. The vector and the pointers it contains will be copied. The objects
they point to won't.

If I want this I'll have to implement my own copy constructor... i.e.
I'll have to implement X(X&) and operator= on X, right?

Well, the copy constructor is probably better X(const X&), but yes, you will
need that. You'll probably also need to define a destructor that deletes
the objects. This is called "The Rule of Three". If you need one of a copy
constructor, copy assignment operator and destructor, you probably need all
three of them.

 

[Fei Liu]

Hi all,

Imagine I have:
class X {
public:
// Some methods...

private:
vector<MyObject*> vec;

};

I think that the default copy constructor will just copy an object of
this class into a new one where vec is new by the pointers inside vec
will point to the exact same place as the original one, right? It'll
not copy MyObject also, right?

If I want this I'll have to implement my own copy constructor... i.e.
I'll have to implement X(X&) and operator= on X, right?

If you found you need to implement your own copy constructor, then
follow the rule of 3, also implement your copy assignment operator and
destructor.