构建器

//只有当你的产品非常复杂，需要大量的配置时，使用Builder模式才有意义。//下面的两个产品是相关的，尽管它们没有共同的接口。class Car是//一辆车可以有GPS，旅行电脑和一定数量的//座位。不同型号的汽车(跑车、SUV、//敞篷车)可能安装或启用了不同的功能。每辆车都应该有一本用户手册，对应于汽车的配置，并描述了它的所有功能。//构建器接口指定了创建产品对象不同部分的方法。interface Builder is method reset() method setSeats(…)method setEngine(…)method setTripComputer(…)method setGPS(…)你的//程序可能有几个不同的构建器，每个//实现不同。car //一个新的构建器实例应该包含一个空白的产品//对象，它将在进一步的组装中使用。// reset方法清除正在构建的对象。 method reset() is this.car = new Car() // All production steps work with the same product instance. method setSeats(...) is // Set the number of seats in the car. method setEngine(...) is // Install a given engine. method setTripComputer(...) is // Install a trip computer. method setGPS(...) is // Install a global positioning system. // Concrete builders are supposed to provide their own // methods for retrieving results. That's because various // types of builders may create entirely different products // that don't all follow the same interface. Therefore such // methods can't be declared in the builder interface (at // least not in a statically-typed programming language). // // Usually, after returning the end result to the client, a // builder instance is expected to be ready to start // producing another product. That's why it's a usual // practice to call the reset method at the end of the // `getProduct` method body. However, this behavior isn't // mandatory, and you can make your builder wait for an // explicit reset call from the client code before disposing // of the previous result. method getProduct():Car is product = this.car this.reset() return product // Unlike other creational patterns, builder lets you construct // products that don't follow the common interface. class CarManualBuilder implements Builder is private field manual:Manual constructor CarManualBuilder() is this.reset() method reset() is this.manual = new Manual() method setSeats(...) is // Document car seat features. method setEngine(...) is // Add engine instructions. method setTripComputer(...) is // Add trip computer instructions. method setGPS(...) is // Add GPS instructions. method getProduct():Manual is // Return the manual and reset the builder. // The director is only responsible for executing the building // steps in a particular sequence. It's helpful when producing // products according to a specific order or configuration. // Strictly speaking, the director class is optional, since the // client can control builders directly. class Director is // The director works with any builder instance that the // client code passes to it. This way, the client code may // alter the final type of the newly assembled product. // The director can construct several product variations // using the same building steps. method constructSportsCar(builder: Builder) is builder.reset() builder.setSeats(2) builder.setEngine(new SportEngine()) builder.setTripComputer(true) builder.setGPS(true) method constructSUV(builder: Builder) is // ... // The client code creates a builder object, passes it to the // director and then initiates the construction process. The end // result is retrieved from the builder object. class Application is method makeCar() is director = new Director() CarBuilder builder = new CarBuilder() director.constructSportsCar(builder) Car car = builder.getProduct() CarManualBuilder builder = new CarManualBuilder() director.constructSportsCar(builder) // The final product is often retrieved from a builder // object since the director isn't aware of and not // dependent on concrete builders and products. Manual manual = builder.getProduct()