面向对象系统分析与设计_装饰器模式.ppt

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1、17七月2021NeusoftComputerScienceandTechnologyDepartmentcopyright1OOSystemAnalysis&Design【TheDecoratorPattern】17七月2021NeusoftComputerScienceandTechnologyDepartmentcopyright2Enjoycoffee…17七月2021NeusoftComputerScienceandTechnologyDepartmentcopyright3Ourjobis:TohelpStarbuzzCoffeeCafétoupdatetheiro

2、rderingsystem.17七月2021NeusoftComputerScienceandTechnologyDepartmentcopyright4ThegoalistoComputethecostofthebeverage;Givethedescriptionofthebeverage;17七月2021NeusoftComputerScienceandTechnologyDepartmentcopyright5Coffeewithlayers17七月2021NeusoftComputerScienceandTechnologyDepartmentcopyright6St

3、arbuzzCoffeeCoffeesHouseBlend$0.89DarkRoast$0.99Decaf$1.05Espresso$1.99CondimentsSteamedMilk$0.10Mocha$0.20Soy$0.15Whip$0.1017七月2021NeusoftComputerScienceandTechnologyDepartmentcopyright7Classdiagram:BaseBeverage是所有饮料的基类；cost()是抽象方法，所有子类都需要定义它们自己的cost()实现来返回特定饮料的价钱；description变量也是在子类里赋值的，表示特

4、定饮料的描述信息，getDescription()方法可以返这个描述。17七月2021NeusoftComputerScienceandTechnologyDepartmentcopyright817七月2021NeusoftComputerScienceandTechnologyDepartmentcopyright9除了咖啡以为，还提供丰富的调味品，比如：炼乳、巧克力、砂糖、牛奶等，而且这些调味品也是要单独按份收费的，所以调味品也是订单系统中重要的一部分。17七月2021NeusoftComputerScienceandTechnologyDepartmentcopyrig

5、ht10改进后的Beverage基类17七月2021NeusoftComputerScienceandTechnologyDepartmentcopyright1117七月2021NeusoftComputerScienceandTechnologyDepartmentcopyright12Classdiagram:Condiments17七月2021NeusoftComputerScienceandTechnologyDepartmentcopyright13Classdiagram:complete17七月2021NeusoftComputerScienceandTechn

6、ologyDepartmentcopyright14TheDecoratorPatternTheDecoratorPatternattachesadditionalresponsibilitiestoanobjectdynamically.Decoratorsprovideaflexiblealternativetosubclassingforextendingfunctionality.ClassdiagramforDecorator17七月2021NeusoftComputerScienceandTechnologyDepartmentcopyright15Componen

7、t（被装饰对象基类）定义对象的接口，可以给这些对象动态增加职责；ConcreteComponent（具体被装饰对象）定义具体的对象，Decorator可以给它增加额外的职责；Decorator（装饰者抽象类）维护一个指向Component实例的引用，并且定义了与Component一致的接口；ConcreteDecorator（具体装饰者）具体的装饰对象，给内部持有的具体被装饰对象增加具体的职责；17七月2021NeusoftComputerScienceandTechnologyDepart