Question

I have a vector like so:

vector<MyType*> _types;

And I want to iterate over the vector and call a function on each of MyTypes in the vector, but I’m getting invalid return errors from the compiler. It appears the pos iterator isn’t a pointer to MyType, it’s something else. What am I not understanding?

Edit: Some code..

    for (pos = _types.begin(); pos < _types.end(); pos++)
{
    InternalType* inst = *pos->GetInternalType();
}

The compiler errors are:

• invalid return type ‘InternalType**’ for overloaded ‘operator ->’
• ‘GetInternalType’ : is not a member of ‘std::_Vector_iterator<_Ty,_Alloc>’

Edit pt2

Should my vector contain pointers or objects? What are the pros and cons? If I am using new to create an instance, I am guessing I can only use a vector of pointers to MyType is that correct?

Answer 1

If the vector contained objects, not pointers, you could do pos->foo(). The iterator “acts like” a pointer. But your vector contains pointers, so an iterator will act like a pointer to a pointer, so needs to be dereferenced twice.

MyType *pMyType = *pos; // first dereference
if (pMyType) {          // make sure the pointer is not null
  pMyType->foo();       // second dereference
}

If you are sure the pointer is not null, you could do this:

(*pos)->foo();

The parenthesis around *pos are needed so the dereference applies to pos, not to pos->foo(). Order of operations.

If your vector needs to contain items from a class hierarchy (e.g., subclasses of MyType), then you have to make it a vector of pointers. Otherwise a vector of objects is probably simpler.