Iteration through a std::vector

Question

Why is it asking me to overload the operator = ? I have previously iterated through a std::list and I did not have such problems.

class Grup : public Shape {

private:

    std::vector<Shape*> continut;

public:

    static const std::string identifier;

    Grup();
    ~Grup();

    void add(Shape *shape);
    void remove(Shape *shape);
    void output(std::ostream &outs) const;
    void readFrom(std::istream &ins);
    void moveBy(int x, int y);

    friend std::ostream &operator<<(std::ostream &outs, const Grup &grup);
};


std::ostream &operator<<(std::ostream &outs, const Grup &grup)
{

 std::vector<Shape*>::iterator it;

    outs << "Grupul este format din: " << std::endl;

    for (it = continut.begin(); it != continut.end(); it++)
    {

    }    

    return outs;
}

Error: "No viable overload '='. "

Answer 1

(After magnification of the screenshot) grup is being passed in as a const, so begin() will return a const_iterator which cannot be assigned to an iterator.

Change declaration of it to:

std::vector<Shape*>::const_iterator it;

---

Note In C++11 you can use auto to instruct the compiler to deduce the type:

for (auto it = grup.continut.begin(); it != grup.continut.end(); it++)
{
    outs << **s << std::endl;
}

Other alternatives in C++11 are the range-based for loop:

for (auto& shape: grub.continut)
{
    outs << *s << std::endl;
}

or std::for_each() with a lambda:

std::for_each(grub.continut.begin(),
              grub.continut.end(),
              [&](Shape* s) { outs << *s << std::endl; });