c++ - Erasing item in a for(-each) auto loop

Question

Is there a way to erase specific elements when using a auto variable in a for loop like this?

for(auto a: m_Connections)
{
    if(something)
    {
        //Erase this element

    }
}

I know I can either do say

for(auto it=m_map.begin() ...

or

for(map<int,int>::iterator it=m_map.begin() ...

and manually increment the iterator (and erase) but if I could do it with less lines of code I'd be happier.

Thanks!

Answer 1

You can't. A range-based loop makes a simple iteration over a range simpler, but doesn't support anything that invalidates either the range, or the iterator it uses. Of course, even if that were supported, you couldn't efficiently erase an element without access to the iterator.

You'll need an old-school loop, along the lines of

for (auto it = container.begin(); it != container.end();) {
    if (something) {
        it = container.erase(it);
    } else {
        ++it;
    }
}

or a combination of container.erase() and std::remove_if, if you like that sort of thing.