Question

I have a STL map in C++ where the key is an unsigned int, and the value is a class whose constructor is:

Foo::Foo(unsigned int integerValue){
    //Some stuff
}

At other class I have declarated the std::map at the header:

private:
    std::map<unsigned int, Foo> *m_mapFoo;

And at the cpp file I created it and inserted instances of Foo:

m_mapFoo = new std::map<unsigned int, Foo>;
m_mapFoo->insert(0, new Foo(0));
m_mapFoo->insert(1, new Foo(1));

But I’m getting the following error at the insert methods:

no matching function for call to ‘std::map<unsigned int, Foo, std::less<unsigned int>, std::allocator<std::pair<const unsigned int, Foo> > >::insert(const unsigned int&, Foo*)’

Similar problem at find method:

m_mapFoo.find(0)->second->someFunctionIntoFooClass();

Where the error is exactly the following:

request for member ‘find’ in ‘((Foo*)this)->Foo::m_mapGeoDataProcess’, which is of non-class type ‘std::map<unsigned int, Foo, std::less<unsigned int>, std::allocator<std::pair<const unsigned int, Foo> > >*’

Additional notes: I don’t have a Foo copy constructor, but I don’t think that’s the problem.

Any help understanding this errors?

Answer 1

You have a pointer to a map containing Foo values

std::map<unsigned int, Foo> *m_mapFoo;

and you are treating it as if it contained Foo pointer values:

std::map<unsigned int, Foo*> *m_mapFoo;

Try this:

m_mapFoo = new std::map<unsigned int, Foo>;
m_mapFoo->insert(std::make_pair(0, Foo(0)));
m_mapFoo->insert(std::make_pair(1, Foo(1)));

As for the second error, you have a pointer to a map, so you need

std::map<unsigned int, Foo>::iterator it = m_mapFoo->find(0);
if (it) {
  it->second.someFunctionIntoFooClass();
} else {
  // entry not found
}