总是使抽象父类实现一个接口。模板方法设计模式在框架设计中特别有价值(在这章的结尾讨论了)。
Always make the abstract parent class implement an interface. The Template Method design pattern is especially valuable in framework design (discussed towards the end of this chapter).
模板方法设计模式(gof)强调了一个普遍的问题：我们知道算法的每一步，并且知道他们执行的顺序，但是我们不知道怎么样去执行所有的这些步骤。
The Template Method design pattern (GoF) addresses a common problem: we know the steps of an algorithm and the order in which they should be performed, but don't know how to perform all of the steps.
策略设计模式比模板方法模式花费了更多的工作去实现，但是它也更灵活。
The Strategy design pattern takes a little more work to implement than the Template Method pattern, but it is more flexible.
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