c++ this pointer

If I''m understanding your question correctly, in the constructor for class A, you can always use the this pointer as a pointer to a valid class A object, though not necessarily as a pointer to an object of a descendant class.

What about to another object say

in class A''s constructor

A
{
    b = new B(this);
}

where B* b is declared a member of A.

I think that is possible. Because once you''re in the brackets the object is already constructed.
I would be very weird if you would use the this pointer in the initialization of a B object, like this:

// This is assuming the constructor of B takes an argument 

// of type A*

A::A : b(this)
{
}

Would that work?

It would work fine as long as b doesn''t try to access any of the methods in a i.e. a->DoSomething(). It''s fine to just store away the pointer for later use.

James

quote:

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Original post by gommo
What about to another object say

in class A''s constructor

A
{
    b = new B(this);
} 

where B* b is declared a member of A.

---

This is legal, but not necessarily smart programming. Whether or not it does bad things depends on how the B''s constructor uses the pointer. If all B does is store the pointer, things are probably fine. Otherwise Bad Things™ might happen.

quote:

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A::A : b(this)
{
} 

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This isn''t legal. (Though some compilers will let you do it with only a warning). The this pointer isn''t valid until you get inside the brackers.