Chapter 20 Object-Oriented Concepts and Principles

1. Chapter 20Object-Oriented Conceptsand Principles

2. The OO Process Model

3. The OO Mindset objects problem domain

4. Key Concepts • classes and class hierarchies • instances • inheritance • abstraction and hiding • objects • attributes • methods • encapsulation • polymorphism • messages

5. Classes • object-oriented thinking begins with the definition of a class often defined as: • template • generalized description • pattern • “blueprint” ... describing a collection of similar items • a metaclass (also called a superclass) is a collection of classes -- hmmmmmmmmm • once a class of items is defined, a specific instance of the class can be defined

6. Building a Class

7. What is a Class? occurrences roles organizational units things places external entities structures class name attributes: operations:

8. method # 2 method # 1 data method # 6 method # 4 method # 5 Achieves“information hiding” Encapsulation/Hiding Theobject encapsulates both data and the logical procedures required to manipulate the data

9. furniture (superclass) table chair desk "chable" subclasses of the furniture superclass instances of chair Class Hierarchy

10. Messages