static

• The reserved static has several uses in C++
• The simplest is to extend the lifetime of a variable.
  • reference
  • These are variables that are local to a function.
  • The definition is proceeded by the keyword static

  • function Foo() {
        static int callCount{0};
    
    } 

  • On first call to the function
    • The variable is initialized.
    • Or the constructor if it is a class.
  • When the function exits, the static variable does NOT go out of lifetime.
  • The value is preserved across calls.
  • The destructor is only called when the program exits.
• This can be extended to classes as well.
  • But the operation is different.
  • Static data members shared across all instances of a class.
  • Static member DO NOT need a instance of the class to be created to be called.
• Static member functions are discussed on 306
  • They are shared across all instances of the class.
  • They do have access to static members.
  • But they don't have access to non-static member variables.
  • Or the *this pointer
  • Or anything else that is part of an individual instance of a class.
• Static constants
  • Must be initialized when declared but
  • Ints no problem.
  • Others must either be
    • inline
    • Or declared outside of the class declaration block.
• Static members are discussed on 314
  • Again shared across all instances.
  • Can be declared inline or outside of the block.
• But why do I want this?
• Look at the chapter on debugging (P 1050)
• I have an abbreviated version in the code directory