Inheritance Basics

• often we want small adaptations
• we want to extend existing behavior and state
• solution: class inheritance
• a class extends the definition of its superclass

a subclass

• can add state and behavior:
  • color, borderColor, ...
• can use superclass behavior and state
• can specialize and redefine superclass behavior

• Object is the root of most classes
• ProtoObject (Object's superclass) is for special purposes...
  • ...but we will ignore it as it is not important

• happens during class definition
• computed from
  • the class own instance variables
  • the ones of its superclasses

• happens at runtime
• the method is searched
  • starting from the receiver's class
  • then going to the superclass

• happens at runtime
• the method is searched
  • starting from the receiver's class
  • then going to the superclass