設計模式學習-建造者模式

敖老黑發表於2018-01-04
設計模式

基本概念

建造者模式主要用於分離物件的建立和配置。呼叫元件負責提供資料。並負責將配置資料傳遞給建造者。建造者代替呼叫元件去建立響應的物件。

好處

  • 使修改物件的預設值變簡單
  • 呼叫元件無需關心太多物件的構建過程

何時使用

  • 物件建立需要進行復雜的配置。構造過程複雜。不想預設配置分散到程式的各個角落，此時可以使用建造者模式

示例程式

新建一個名為Builder的 OSX命令列程式

實現如下程式碼

///Food.swift
class 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.swift
final 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.swift
let builder = BurgerBuilder()

let burger:Burger = builder
    .setVeggie(true)
    .setMayo(false)
    .setCooked(.wellDone)
    .addPatty(false)
    .buildBurgerObject(name: "Joe")


burger.printDescription()
複製程式碼

輸出結果

Name Joe
Vegie true
Patties 2
Pickles false
Mayo false
Ketchup true
Cook Well Done
複製程式碼

上面程式碼中設定屬性的方法返回值可以不寫。這裡這麼寫為了實現鏈式呼叫。

  • cocoa中建造者模式的應用
//// cocoa 中 建造者模式的應用
var dateBuilder = DateComponents()
dateBuilder.hour = 10
dateBuilder.day = 6
dateBuilder.month = 9
dateBuilder.year = 1950
dateBuilder.calendar = Calendar(identifier: .gregorian)


if let date = dateBuilder.date {
    print(date)
}

複製程式碼

輸出結果:

1950-09-06 02:00:00 +0000
複製程式碼

程式碼下載地址github.com/RockyAo/Des…

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