2、GRASP原则二：信息专家 Information Expert
What is a general principle of assigning responsibility to objects?
为一个对象 分配职责的一般原则是什么？
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2.2 GRASP rule2: Information Expert
Name: Information Expert (信息专家)
Problem:
What is a general principle of assigning responsibility to objects?
Solution:
Assign responsibility to the class that has the information necessary to fulfill responsibility
Information
an object's own state,
about other objects, the world around an object,
information the object can derive,
and so forth
Answer to Mini exercise 2
2.3 Information Expert — How to?
步骤
1）Clearly state the responsibility
2）Look in Design Model for relevant classes
3）Else look in Domain Model and create design classes
信息专家的优点
封装性 Encapsulation
对象充分利用自身的信息 objects support their own information
支持低耦合 supports low coupling
系统行为分布到不同的类 Behavior is distributed across classes
支持高内聚 supports high cohesion