swift - The Builder Pattern

利用类构造函数默认参数，创建一个类。

之所以用Builder Pattern是因为要根据不同属性来创建不同的对象。

正如如下步骤：1.name 2.选择一个产品 3.客户定制一个产品

client:

// Step 1 - Ask for name

let name ="Joe";

// Step 2 - Select a Product

let builder =BurgerBuilder.getBuilder(Burgers.BIGBURGER);

// Step 3 - Customize burger?

builder.setMayo(false);

builder.setCooked(Burger.Cooked.WELLDONE);

let order =builder.buildObject(name);

order.printDescription();

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

pattern:

enum Burgers {

case STANDARD; case BIGBURGER;case SUPERVEGGIE;

}

class BurgerBuilder {

private var veggie =false;

private var pickles =false;

private var mayo =true;

private var ketchup =true;

private var lettuce =true;

private var cooked =Burger.Cooked.NORMAL;

private var patties =2;

private var bacon =true;

private init() {

// do nothing

}

func setVeggie(choice: Bool) {

self.veggie = choice;

if (choice) {

self.bacon =false;

}

}

func setPickles(choice: Bool) { self.pickles = choice; }

func setMayo(choice: Bool) { self.mayo = choice; }

func setKetchup(choice: Bool) { self.ketchup = choice; }

func setLettuce(choice: Bool) { self.lettuce = choice; }

func setCooked(choice: Burger.Cooked) { self.cooked = choice; }

func addPatty(choice: Bool) { self.patties = choice ?3 : 2; }

func setBacon(choice: Bool) { self.bacon = choice; }

func buildObject(name: String) -> Burger {

return Burger(name: name,veggie:veggie,patties: patties,

pickles:pickles,mayo: mayo,ketchup:ketchup,

lettuce:lettuce,cook: cooked,bacon:bacon);

}

class func getBuilder(burgerType:Burgers) ->BurgerBuilder {

var builder:BurgerBuilder;

switch (burgerType) {

case .BIGBURGER: builder = BigBurgerBuilder();

case .SUPERVEGGIE: builder = SuperVeggieBurgerBuilder();

case .STANDARD: builder = BurgerBuilder();

}

return builder;

}

}

class BigBurgerBuilder :BurgerBuilder {

private override init() {

super.init();

self.patties =4;

self.bacon =false;

}

override func addPatty(choice:Bool) {

fatalError("Cannot add patty to Big Burger");

}

}

class SuperVeggieBurgerBuilder :BurgerBuilder {

private override init() {

super.init();

self.veggie =true;

self.bacon =false;

}

override func setVeggie(choice:Bool) {

// do nothing - always veggie

}

override func setBacon(choice:Bool) {

fatalError("Cannot add bacon to this burger");

}

}

（编辑：李大同）

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