Go 語言 設計模式-生成器模式

生成器是一種建立型設計模式， 使你能夠分步驟建立複雜對象。

與其他建立型模式不同， 生成器不要求産品擁有通用接口。 這使得用相同的建立過程生成不同的産品成為可能。

概念示例

當所需産品較為複雜且需要多個步驟才能完成時， 也可以使用生成器模式。 在這種情況下， 使用多個構造方法比僅僅使用一個複雜可怕的構造函數更簡單。 分為多個步驟進行建構的潛在問題是， 建構不完整的和不穩定的産品可能會被暴露給用戶端。 生成器模式能夠在産品完成建構之前使其處于私密狀态。

iBuilder.go: 生成器接口

package main

type IBuilder interface {
    setWindowType()
    setDoorType()
    setNumFloor()
    getHouse() House
}

func getBuilder(builderType string) IBuilder {
    if builderType == "normal" {
        return newNormalBuilder()
    }

    if builderType == "igloo" {
        return newIglooBuilder()
    }
    return nil
}      

normalBuilder.go: 具體生成器

package main

type NormalBuilder struct {
    windowType string
    doorType   string
    floor      int
}

func newNormalBuilder() *NormalBuilder {
    return &NormalBuilder{}
}

func (b *NormalBuilder) setWindowType() {
    b.windowType = "Wooden Window"
}

func (b *NormalBuilder) setDoorType() {
    b.doorType = "Wooden Door"
}

func (b *NormalBuilder) setNumFloor() {
    b.floor = 2
}

func (b *NormalBuilder) getHouse() House {
    return House{
        doorType:   b.doorType,
        windowType: b.windowType,
        floor:      b.floor,
    }
}      

iglooBuilder.go: 具體生成器

package main

type IglooBuilder struct {
    windowType string
    doorType   string
    floor      int
}

func newIglooBuilder() *IglooBuilder {
    return &IglooBuilder{}
}

func (b *IglooBuilder) setWindowType() {
    b.windowType = "Snow Window"
}

func (b *IglooBuilder) setDoorType() {
    b.doorType = "Snow Door"
}

func (b *IglooBuilder) setNumFloor() {
    b.floor = 1
}

func (b *IglooBuilder) getHouse() House {
    return House{
        doorType:   b.doorType,
        windowType: b.windowType,
        floor:      b.floor,
    }
}      

house.go: 産品

type House struct {
    windowType string
    doorType   string
    floor      int
}      

director.go: 主管

package main

type Director struct {
    builder IBuilder
}

func newDirector(b IBuilder) *Director {
    return &Director{
        builder: b,
    }
}

func (d *Director) setBuilder(b IBuilder) {
    d.builder = b
}

func (d *Director) buildHouse() House {
    d.builder.setDoorType()
    d.builder.setWindowType()
    d.builder.setNumFloor()
    return d.builder.getHouse()
}      

main.go: 用戶端代碼

package main

import "fmt"

func main() {
    normalBuilder := getBuilder("normal")
    iglooBuilder := getBuilder("igloo")

    director := newDirector(normalBuilder)
    normalHouse := director.buildHouse()

    fmt.Printf("Normal House Door Type: %s\n", normalHouse.doorType)
    fmt.Printf("Normal House Window Type: %s\n", normalHouse.windowType)
    fmt.Printf("Normal House Num Floor: %d\n", normalHouse.floor)

    director.setBuilder(iglooBuilder)
    iglooHouse := director.buildHouse()

    fmt.Printf("\nIgloo House Door Type: %s\n", iglooHouse.doorType)
    fmt.Printf("Igloo House Window Type: %s\n", iglooHouse.windowType)
    fmt.Printf("Igloo House Num Floor: %d\n", iglooHouse.floor)

}      

output.txt: 執行結果

Normal House Door Type: Wooden Door
Normal House Window Type: Wooden Window
Normal House Num Floor: 2

Igloo House Door Type: Snow Door
Igloo House Window Type: Snow Window
Igloo House Num Floor: 1