Access Modifiers and Friends

• This is chapter 8. Read it.
  • This is a detailed review of classes.
  • I am only going to hit the points I feel need emphasized.
• Here is an example of an exception class in a header and a cpp file
  • Note, override is only used once, in the headers.
  • This occurs occasionally with other words as well.
  • We will discuss these further soon.
  • DansExceptT.h
  • DansExceptT.cpp
• Declare members that do not change this as const
• Access Control
  • What does public mean?
    • Everything can get access to public members.
  • What does private mean?
    • Only instances of the class can access private members.
    • Oh, and friends.
  • We will discuss protected later.
    • It relates to inheritance.
    • Derived classes are allowed to access protected members of the base class.
    • Non-derived classes can not get at protected members of the base class.
  • Access controls can be declared multiple times and in any order.
    • But it is generally better to keep them grouped.
• Access control can be overcome by friend
  • This is at the beginning of chapter 9
  • Declaring a class or function to be a fried overrides the access controls.
• Gregorie says that friends are
  • Easy to abuse
  • Break encapsulation.
• Scott Meyer is very opposed to friend functions.
  • He says that the more "things" that have access to private data the greater the impact if something changes.
  • Thus friends provide a huge hole where things can become really broken on a change.
  • He comes close to suggesting you never use them.
• Think about changing a private variable name
  • How many places should you have to edit to accomplish this
    1. The class header file.
    2. The class implementation.
    3. EVERY friend function/class.
• Meyers says to declare all member data private.
• Notice in these examples, class members are initialized at definition
  • int data {value};
  • This has become a preferred way to initialize data.