Question

Possible Duplicate:
Elegant solution to duplicate, const and non-const, getters?

Say I have a c++ class with a memberfunction which is overloaded for const, like this:

        Type*  DoSomething();
const   Type*  DoSomething() const;

If this is a larger, more complex member, how does one prevent having to write the same code twice ? Can’t call any non-const functions from the const one. And calling the const version from the non-const one results in a const pointer wich has to be cast to non-const (wich smells a bit imo).

Answer 1

You can delegate to a template static member function, as in:

class Widget
{
    Type member;

    template<typename Result, typename T>
    static Result DoSomethingImpl(T This)
    {
        // all the complexity sits here, calculating offsets into an array, etc
        return &This->member;
    }

public:
            Type*  DoSomething() { return DoSomethingImpl<Type*>(this); }
    const   Type*  DoSomething() const { return DoSomethingImpl<const Type*>(this); }
};

In C++11, you can even get rid of the non-inferred template argument, with:

static auto DoSomethingImpl(T This) -> decltype(This->member)