Passing unnamed classes through functions

Question

How do I pass this instance as a parameter into a function?

class
{
    public:
    void foo();
} bar;

Do I have to name the class?
It

Answer 1

Why should you create an anonymous class when you want to pass it to a function?

Just explicitly declare the class:

class Foo {
  // ...
};

void Method(Foo instance); 

int main() {
    Foo bar;
    Method(bar);
}

The 2nd possibility would be using a template-function, so the compiler would infer the type (Note that this is not standard-compatible!)

#include 

using namespace std;

template 
void SayFoo(T& arg) {
    arg.Foo();
}

int main() {

    class {
    public: 
        void Foo() { cout << "Hi" << endl; }
    } Bar;

    Bar.Foo();

    SayFoo(Bar);

    return 0;
}

There is no problem with copying the class since the compiler generated the copy constructor automatically and you can use tools like boost::typeof in order to avoid referring to the type explicitly.

BOOST::AUTO(copy, Bar);

Another approch is using (relatively slow) runtime-polymorphism (interfaces/inheritance).