What is the difference between "::" "." and "->" in c++

Question

Possible Duplicate:
When do I use a dot, arrow, or double colon to refer to members of a class in C++?

I have created the class called Kwadrat and I have three int fields inside. The Code Blocks gives me advice that i can get into the field of the object by ::, . and ->. The arrow is the one that only works, but why? What's the difference between those three?

#include <iostream>

using namespace std;

class Kwadrat{
public:
int val1, val2, val3;
    Kwadrat(int val1, int val2, int val3)
    {
        this->val1 = val1;
        //this.val2 = val2;
        //this::val3 = val3;
    }
};

int main()
{
    Kwadrat* kwadrat = new Kwadrat(1,2,3);
    cout<<kwadrat->val1<<endl;
    cout<<kwadrat->val2<<endl;
    cout<<kwadrat->val3<<endl;
    return 0;
}

Answer 1

1.-> for accessing object member variables and methods via pointer to object

Foo *foo = new Foo();
foo->member_var = 10;
foo->member_func();

2.. for accessing object member variables and methods via object instance

Foo foo;
foo.member_var = 10;
foo.member_func();

3.:: for accessing static variables and methods of a class/struct or namespace. It can also be used to access variables and functions from another scope (actually class, struct, namespace are scopes in that case)

int some_val = Foo::static_var;
Foo::static_method();
int max_int = std::numeric_limits<int>::max();