Today ,I read the chapter one of the Head first design pattern,and i found the book was a exicting book.
now i just want to sum it up.
The chapter one tell us a pattern called Strategy pattern,Frist of all ,we should know the formal
definition of the pattern, Here is it .the Strategy pattern defines a family of algorithms , encapsulate
each one , and makes them interchangeable.do as this , a algorithm will vary independently from the
clients that use it .
The point of this pattern is finding out the changable parts from the system,and encapsulating them
into a independent unit .In the concrete project,what we need to do is finding chang- es and encapsulating
them into a class or a interface.and the client only know the abstract class or interface ,and don't need
take care of the implementments.
This pattern relate to three roles, one is the context part ,another is the abstract strategy part ,and
the rest one is the concrete strategy part .what we need to do just is implement the concrete
strategy ,what'more ,the context don't need to know the concrete implements.Here is the class Diagram
.
This chapte also tell us some oo design principles.As are show here.
1 . identify the aspects of your app that vary and separate them from what stays the same.
2 . Program to interface ,not to implementation.
3 . Favor compositon over inheritance .