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

Use following trick:

class Bar;
class Foo {
public:  
  Bar* bar() { 
    // non-const case
    /* code that does something */ 
  }  
  const Bar* bar() const {    
      return This().bar();  // use non-const case
   }

private:
  //trick: const method returns non-const reference
  Foo & This() const { return const_cast(*this); } 
};

Note it is possible to use unique function This for any const/non-const functions.

Alternative solution without static_cast (but I prefer the first one):

class Bar;
class Foo {
public:  
  const Bar* bar() const { /* code that does something */ }  
  Bar* bar() { return const_cast(cthis().bar()); } // use const case
private:
  const Foo & cthis() const { return *this; } 
};