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(C++) Avoid duplication in const and non-const member functions

 

In good method design, avoid duplication in const and non-const member functions [1,2]. Instead, have the non-const method call the const method.

 

#include <vector>
#include <cassert>

struct StoreTenInts
{
  StoreTenInts() : mV(std::vector<int>(10,0)) {}

  int& operator[](const int i)
  {
    //Calls the const version of operator[]
    //To avoid duplication in const and non-const member functions [1]
    return const_cast<int&>(const_cast<const StoreTenInts&>(*this)[i]);
  }
  const int& operator[](const int i) const
  {
    //The actual work of operator[]
    assert(i >= 0 && i < 10);
    return mV[i];
  }

  private:
  std::vector<int> mV;
};

 

 

 

 

 

References

 

  1. Herb Sutter, Andrei Alexandrescu. C++ coding standards: 101 rules, guidelines, and best practices. 2005. ISBN: 0-32-111358-6. Chapter 94: 'Avoid casting away const', item 'Exceptions'
  2. Scott Meyers. Effective C++ (3rd edition). ISBN: 0-321-33487-6. Item 3, paragraph 'Avoid duplication in const and non-const member functions'

 

 

 

 

 

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