“The Rule of The Big Four (and a half)" states that if you implement one of
- The copy constructor
- The assignment operator
- The move constructor
- The destructor
- The swap function
then you must have a policy about the others.
Which functions need to implemented, and what should each function's body look like?
- default constructor (which could be private)
- copy constructor (Here you have real code to handle your resource)
move constructor (using default constructor and swap) :
S(S&& s) : S{} { swap(*this, s); }
assignment operator (using constructor and swap)
S& operator=(S s) { swap(*this, s); }
destructor (deep copy of your resource)
- friend swap (doesn't have default implementation :/ you should probably want to swap each member). This one is important contrary to the swap member method:
std::swap uses move (or copy) constructor, which would lead to infinite recursion.
