Question

I have these three related class members:

vector<Frame*>* poolFrames;
vector<Frame*>*::iterator frameIterator;
vector<vector<Frame*>::iterator>* poolFrameIterators;

When I compile, gcc tells me

error: invalid use of ‘::’
error: expected ‘;’ before ‘frameIterator’

In reference to the middle line, where I define frameIterators. It goes away when I loose the pointer to the vector and make it a vector::iterator. However, I want them to be pointers. Is there a special way to define the data type that I want, or do I need to use vector::iterator and then dereference?

Answer 1

I see what you were trying to do. You’ve defined poolFrames as a pointer to a vector. Then you want to define frameIterator as an iterator for poolFrames. Since poolFrames is a pointer, you think you need a special pointer-to-vector iterator, but you’re mistaken.

A vector iterator is a vector iterator is a vector iterator, no matter how you managed to refer to the vector in the first place. You need frameIterator to be a simple iterator:

vector<Data*>::iterator frameIterator;

To assign a value to that variable, you’ll need to dereference your vector pointer, like this:

frameIterator = poolFrames->begin();

If poolFrames were a vector instead of a pointer to a vector, you’d use the dot operator instead: poolFrames.begin().