Copy Constructors, Destructors

• Continuing in chapter 8.
  • As we have seen, copy constructors are used to pass by value.
  • If you don't want a copy constructor, delete it.
  • Reference Variables in general
    • Pass by reference, return by reference or otherwise.
    • These behave in a way different from other variables.
      • The initial assignment is a pointer assignment.
      • A pointer to the object is copied to the reference variable.
      • After this, all access are a dereference.
    • We get the cost of a pointer with the ease of a non-pointer.
    • A reference can also be thought of as an alias.
    • See simpleRef.cpp
    • This is efficient as we have discussed for pass by reference, and pass by constant reference parameters.
    • This model has two implications
      • We can have member variables that are references.
        • But they must be assigned in the ctor-initializer
        • Otherwise this is not the first assignment
        • This would be useful if every sector needed a pointer back to the map.
      • We need to be careful that when we return a reference, we are not returning temporary memory.
      • See returnDemo.cpp
    • There is more on this in chapter 11.
  • Object Destruction
    • Objects are destroyed as they are removed from the stack.
    • So in reverse order of creation.
    • This is true for member objects as well
      • The class destructor is called and executed.
      • The the destructors for member objects are called
        • In reverse order of declaration.
    • For my demo I need a static member data
      • This is discussed in chapter 9.
      • But the idea is just like a state member function
        • They exist outside the existence of any particular instance.
        • As such, they need to be initialized is a special way
          • Either class::member=value where you define functions. (Pre c++17)
          • Or static inline type identifer = value in the declaration.
        • See destructor.cpp