How to generate a non-const method from a const method?

Question

While striving for const-correctness, I often find myself writing code such as this

class Bar;

class Foo {
public:
  const Bar* bar() const { /* code that gets          


        

Answer 1

Another way could be to write a template that calls the function (using CRTP) and inherit from it.

template
struct const_forward {
protected:
  // forbid deletion through a base-class ptr
  ~const_forward() { }

  template
  R *use_const() {
    return const_cast( (static_cast(this)->*pf)() );
  }

  template
  R &use_const() {
    return const_cast( (static_cast(this)->*pf)() );
  }
};

class Bar;

class Foo : public const_forward {
public:
  const Bar* bar() const { /* code that gets a Bar somewhere */ }
  Bar* bar() { return use_const(); }
};

Note that the call has no performance lost: Since the member pointer is passed as a template parameter, the call can be inlined as usual.