Cout向量地址

Question

I'm new to this website and a bit new in programming. I'm using vector for the first time and I want to print content of it but I'm getting addresses instead of normal words. I don't know how to do that in other way than this.

My vector:

vector<Component*> vect;

and my code for printing:

void Frame::print() {
    for (int i = 0; i < vect.size(); i++)
        cout << vect[i] << endl;
}

Answer 1

You are storing pointers in your vector. The value of a pointer is a memory address, therefore you are seeing addresses in your output. You need to dereference the pointers to access the actual Component objects:

void Frame::print()
{
    for (int i = 0; i < vect.size(); i++)
    {
        Component *component = vect[i];
        cout << *component << endl; // <-- not the extra '*'
    }
}

In order for this to work, an operator<< overload for Component is also required:

ostream& operator<<(ostream &out, const Component &comp)
{
    // print comp values to out as needed...
    return out;
}

Recommended reading:

Operator overloading

You also need to study up on pointers and references in general.

Answer 2

vect is a vector (aka a lump of contiguous storage) of Component * (aka Component pointers) that is it's a chunk of memory with addresses of other chunks of memory which the compiler will treat as a Component class object. Printing those addresses via cout will just give you a big list of meaningless numbers.

What I suspect you want to do is probably not store a vector of Component pointers at all and just store a vector of Components. It's frowned upon in C++ these days to store raw pointers unless you know exactly what you are doing. If you really do want pointers you should use a vector of std::unique_ptr and std::make_unique.

Once you start trying to print Components rather than addresses of them you will most likely see that there is no << operator for Component. You will need to write one. Something like

std::ostream& operator<<(std::ostream &stream, const Component&component)
{
  stream << component.string_member;
  return stream;
}