课程: Programming Foundations: Design Patterns

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Limitations of inheritance

Limitations of inheritance

课程: Programming Foundations: Design Patterns

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Limitations of inheritance

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- [Instructor] What we really need at this point is an example to demonstrate the problems with inheritance, so let's take a look at a class design for a duck simulator. Let's say we want to design a duck simulator. To do that we need a set of Duck classes. It would be natural to think that you could start with a Duck superclass. You might give the superclass a quack method and a swim method because those are the things that you'd guess all ducks are going to want to do. Let's also give it a display method. But we'll keep that abstract meaning each subclass will need to implement it because each duck will want to implement its own unique appearance. Now because display is abstract, that makes our duck class abstract too meaning that we cannot instantiate a duck directly. To create a duck, we need some concrete classes. Let's add a concrete class MallardDuck and implement its display method so it looks like a mallard.…

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