1 概念

構建者模式定義：

將一個複雜物件的構建與它的表示分離，使得同樣的構建過程可以建立不同的表示

構建者模式包含如下角色：

• Product：具體產品
• ConcreteBuilder：具體建造者
• Builder：抽象建造者
• Director：指揮者

讀者可以對比以下構建者類圖理解各種角色的作用

其中ActorController充當指揮者（Director），ActorBuilder充當抽象建造者，HeroBuilder、AngelBuilder充當具體建造者，Actor充當複雜產品。其中ActorController充當指揮者（Director），ActorBuilder充當抽象建造者，HeroBuilder、AngelBuilder和DevilBuilder充當具體建造者，Actor充當複雜產品。

2 go語言實現

2.1 定義產品角色

type Actor struct {
	Type      string
	Sex       string
	Face      string
	Costume   string
	HairStyle string
}

func (a Actor) ShowActorInfo() {
	fmt.Println("角色型別: ", a.Type)
	fmt.Println("角色性別: ", a.Sex)
	fmt.Println("角色面容: ", a.Face)
	fmt.Println("角色服裝: ", a.Costume)
	fmt.Println("角色髮型: ", a.HairStyle)
}
 

2.2 定義抽象建造者角色

type ActorBuilder interface {
	BuildType()
	BuildSex()
	BuildFace()
	BuildCostume()
	BuildHairStyle()
	CreateActor() Actor
}

2.3 定義具體建造者角色

type HeroBuilder struct {
	actor Actor
}

func (hb *HeroBuilder) BuildType() {
	hb.actor.Type = "英雄"
}

func (hb *HeroBuilder) BuildSex() {
	hb.actor.Sex = "男"
}

func (hb *HeroBuilder) BuildFace() {
	hb.actor.Face = "英俊"
}

func (hb *HeroBuilder) BuildCostume() {
	hb.actor.Costume = "盔甲"
}

func (hb *HeroBuilder) BuildHairStyle() {
	hb.actor.HairStyle = "飄逸"
}

func (hb HeroBuilder) CreateActor() Actor {
	return hb.actor
}

type AngelBuilder struct {
	actor Actor
}

func (ab *AngelBuilder) BuildType() {
	ab.actor.Type = "天使"
}

func (ab *AngelBuilder) BuildSex() {
	ab.actor.Sex = "女"
}

func (ab *AngelBuilder) BuildFace() {
	ab.actor.Face = "漂亮"
}

func (ab *AngelBuilder) BuildCostume() {
	ab.actor.Costume = "白裙"
}

func (ab *AngelBuilder) BuildHairStyle() {
	ab.actor.HairStyle = "披肩長髮"
}

func (ab AngelBuilder) CreateActor() Actor {
	return ab.actor
}
 

2.4 定義指揮者角色

type ActorController struct {
	actorBuilder ActorBuilder
}

func (ac *ActorController) Construct() Actor {
	ac.actorBuilder.BuildType()
	ac.actorBuilder.BuildFace()
	ac.actorBuilder.BuildCostume()
	ac.actorBuilder.BuildSex()
	ac.actorBuilder.BuildHairStyle()
	return ac.actorBuilder.CreateActor()
}

由於go中沒有解構函式，使用New方法建立一個指揮者

    func NewActorController(ab ActorBuilder) *ActorController {
    	return &ActorController{
    		actorBuilder: ab,
    	}
    }

2.5 demo呼叫

package main

import (
	"design_pattern/builder"
	"fmt"
)

func main() {
	var tActor builder.Actor
	tHeroBuilder := builder.HeroBuilder{}
	tAngelBuilder := builder.AngelBuilder{}

	tActorController := builder.NewActorController(&tHeroBuilder)
	tActor = tActorController.Construct()
	tActor.ShowActorInfo()

	fmt.Println("========================")

	tActorController = builder.NewActorController(&tAngelBuilder)
	tActor = tActorController.Construct()
	tActor.ShowActorInfo()
}

讀者可以結合程式碼對照前面的UML類圖理解