Foreach through a vector containing pointers in c++

Question

I made a map filled with vectors which looks like this:

std::map<int, std::vector<CClass*>> pointers = getMap();

And now I want to go through every slot of the map and also through every slot of the vector stored in the map.

This is how it goes through the map:

for (std::map<int, std::vector<CClass*>>::iterator it = pointers.begin(); it != pointers.end(); it++) 

This works fine and it goes through every object just like I want it to.

But now I want to go through every slot in the vector and I tried it like this:

for (std::vector<CClass*>::iterator playerIt = it->second.begin(); playerIt != it->second.end(); playerIt++) 

If I want to access the value stored in it the compiler gives me this error:

file.cpp(552) : error C2839: Ungültiger Rückgabetyp 'CClass **' für überladenen Operator '->'

Which means "invalid return-type 'CClass **' for overweight operator '->'

regards

Answer 1

You can use range-based for loops in C++11 to handle this more readably

for (auto& element : pointers)
{
    for (auto& player : element.second)
    {
        // player will be a CClass* that you can use
        std::string name = player->GetName();  // For example
    }
}

Answer 2

playerIt is an iterator, not a pointer to a CClass . You need to dereference the iterator to get a pointer to CClass :

CClass * player = (*playerIt);
player->ClassMethod(...); // or whatever

Answer 3

playerIt is an iterator that returns a CClass* , but you dereference the iterator via operator->, so you need to dereference the pointer that is returned by the iterator.

So you are possibly saying playerIt->cclass_method() when you should be saying (*playerIt)->cclass_method();

Of course, storing shared_ptr<>, or unique_ptr objects in your vector might be better and easier to understand, along with using typedef to alias the vector<> part of the map.