Polymorphism and Inheritance

1. Polymorphism and Inheritance

2. Overview • Understanding Inheritance • Designing an Inheritance Tree • What does inheritance really help with • Polymorphism

3. Understanding Inheritance • Sometimes a class is to general and it is useful to have a more specific class for a purpose. • This class can inherit functions and values from a parent • Functions can be replaced with specialize versions

4. Understanding Inheritance • Parent • Animal • Children • Fish • Dog

5. Designing an Inheritance Tree • If you have multiple objects that need to inherit from other objects you need and inheritance tree • Inheritance trees show which objects are sub classes to other objects • They show what methods are overridden at each level

6. Overriding Methods • When you have a class tree, the lowest method or most specific method is called first. wolf.roam calls from class Canine wolf.eat calls from class Wolf, not class Animal llama.eat calls from class Animal, not class Wolf

7. What does inheritance really help with • In summary the concept of inheritance: • Allows for reducing duplicate code • Allows for the definition of a common protocol for a group of objectsprotocol (def.): The established code of procedure or behavior in any group, organization, or situation. • Polymorphism

8. Polymorphism • Polymorphism lets you link a super class object reference to a subclass object.

9. More Polymorphism Animal animals[4]; animals[0] = new Dog(); animals[1] = new Cat(); animals[2] = new Lion(); ..... for(int i = 0; i<4; i++){ animals[i].eat(); animals[i].roam(); }

10. More Polymorphism classVet { public void giveShot(Animal a){ // Give animal a shot a.makeNoise(); } }

11. Example • polymorph.cpp • We will create several animal classes that inherit from the base 'Animal' class • We will look at how an 'Animal' pointer can point to any type of animal and still make it work

12. Things to remember • Inheritance is powerful but takes thought • Using overriding makes using multiple object easier • Using overloading gives more versatility to your methods