设计模式学习-建造者模式-白红宇

基本概念

建造者模式主要用于分离对象的创建和配置。调用组件负责提供数据。并负责将配置数据传递给建造者。建造者代替调用组件去创建响应的对象。

好处

使修改对象的默认值变简单

调用组件无需关心太多对象的构建过程

何时使用

对象创建需要进行复杂的配置。构造过程复杂。不想默认配置分散到程序的各个角落，此时可以使用建造者模式

示例程序

新建一个名为Builder的 OSX命令行程序

实现如下代码

///Food.swiftclass Burger {        enum Cooked:String {        case rare = "Rare"        case normal = "Normal"        case wellDone = "Well Done"    }        let customerName:String    let veggieProduct:Bool    let patties:Int    let pickles:Bool    let mayo:Bool    let ketchup:Bool    let cook:Cooked            init(name:String,veggie:Bool,patties:Int,pickles:Bool,         mayo:Bool,ketchup:Bool,lettuce:Bool,cook:Cooked) {                self.customerName = name        self.veggieProduct = veggie        self.patties = patties        self.pickles = pickles        self.mayo = mayo        self.ketchup = ketchup        self.cook = cook    }        func printDescription()  {        print("Name \(customerName)")        print("Vegie \(veggieProduct)")        print("Patties \(patties)")        print("Pickles \(pickles)")        print("Mayo \(mayo)")        print("Ketchup \(ketchup)")        print("Cook \(cook.rawValue)")    }}///BurgerBuilder.swiftfinal class BurgerBuilder {    private var veggie:Bool = false    private var pickles:Bool = false    private var mayo:Bool = true    private var ketchup:Bool = true    private var lettuce:Bool = true    private var cooked:Burger.Cooked = .normal    private var patties:Int = 2        func setVeggie(_ choice:Bool) -> BurgerBuilder{        veggie = choice        return self    }        func setPickles(_ choice:Bool) -> BurgerBuilder {        pickles = choice        return self    }        func setMayo(_ choice:Bool) -> BurgerBuilder {        mayo = choice        return self    }        func setKetchup(_ choice:Bool) -> BurgerBuilder {        ketchup = choice        return self    }        func setLettuce(_ choice:Bool) -> BurgerBuilder {        lettuce = choice        return self    }        func setCooked(_ choice:Burger.Cooked) -> BurgerBuilder {        cooked = choice        return self    }        func addPatty(_ choice:Bool) -> BurgerBuilder {        patties = choice ? 3 : 2        return self    }        func buildBurgerObject(name:String) -> Burger {        return Burger(name: name, veggie: veggie, patties: patties, pickles: pickles, mayo: mayo,                      ketchup: ketchup, lettuce: lettuce, cook: cooked)    }}///main.swiftlet builder = BurgerBuilder()let burger:Burger = builder    .setVeggie(true)    .setMayo(false)    .setCooked(.wellDone)    .addPatty(false)    .buildBurgerObject(name: "Joe")burger.printDescription()复制代码

输出结果

Name JoeVegie truePatties 2Pickles falseMayo falseKetchup trueCook Well Done复制代码

上面代码中设置属性的方法返回值可以不写。这里这么写为了实现链式调用。

cocoa中建造者模式的应用

cocoa 中 建造者模式的应用var dateBuilder = DateComponents()dateBuilder.hour = 10dateBuilder.day = 6dateBuilder.month = 9dateBuilder.year = 1950dateBuilder.calendar = Calendar(identifier: .gregorian)if let date = dateBuilder.date {    print(date)}复制代码

输出结果:

1950-09-06 02:00:00 +0000复制代码

代码下载地址