Object Design

Notes

• This is from chapter 5 of the book.
• Procedural Programming: "What does the program do?"
  • In top down design we ask "What is the main task?"
  • "Can I break this task down into smaller tasks?"
  • And only later "What data do I need to pass to these tasks?"
• Object Oriented Programming: "What real world objects am I modeling"
  • Objects need to have properties and behaviors
  • Objects are instances of classes
  • They have the common behavior, but different properties
    • IE different die objects have different values, but all have a value, and all have the roll behavior.
• Classes are constructed from components.
  • These are the elements that make up the class
  • Including other classes.
• Behaviors are the things that classes can do.
  • Roll, Initialize, get values, ...
• When we start to design a program we can
  • Deign in a purely top down manner, not really acceptable in a class called object oriented programming
  • Go completely object oriented, but probably too much
  • Mix the two, what we will do for now.
• When deciding on building a class you want to have a crisp definition of the class, what it holds and what it does.
  • It must contain properties or data, otherwise it is just an algorithm/function
  • It must contain behaviors otherwise it is just a variable
• Later we will consider some class properties
  • Has-A relationship or composition
  • Is-A relationship or inheritance.