Builder Pattern

Posted on

本文只要讨论了 Builder Pattern 建造者模式的 Go 实现

Builder Pattern 建造者模式

  • 建造者模式将复杂对象的构造及其表示形式分离开来，使得同样的构造过程可以创建不同的表示形式。

抽象接口实现

  • Builder: 创建一个产品（car）对象的各个部件的指定抽象接
  • Interface: 产品（car）功能的抽象接口
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
package car

type Speed float64

const (
	MPH Speed = 1
	KPH       = 1.60934
)

type Color string

const (
	BlueColor  Color = "blue"
	GreenColor       = "green"
	RedColor         = "red"
)

type Wheels string

const (
	SportWheels Wheels = "sports"
	SteelWheels        = "steel"
)

type Builder interface {
	Color(c Color) Builder
	Wheels(w Wheels) Builder
	TopSpeed(s Speed) Builder
	Build() Interface
}

type Interface interface {
	Drive() error
	Stop() error
}

具体产品功能实现

  • 具体产品（car）需继承于 Interface
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
package car

import "fmt"

type car struct {
	Interface
	color  Color
	wheels Wheels
	speed  Speed
}

func (c *car) Drive() error {
	fmt.Printf("A %s car with %s tires is going at %f ", c.color, c.wheels, c.speed)
	if c.speed == MPH {
		fmt.Println("MPH")
	} else {
		fmt.Println("KPH")
	}

	return nil
}

func (c *car) Stop() error {
	fmt.Println("The car stopped.")
	return nil
}

具体建造者功能实现

  • 建造者（carBuilder）需继承于 Builder
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
package car

type carBuilder struct {
	Builder
	c *car
}

func NewCarBuilder() Builder {
	cb := new(carBuilder)
	cb.c = new(car)
	return cb
}

func (cb *carBuilder) Color(c Color) Builder {
	cb.c.color = c
	return cb
}

func (cb *carBuilder) Wheels(w Wheels) Builder {
	cb.c.wheels = w
	return cb
}

func (cb *carBuilder) TopSpeed(s Speed) Builder {
	cb.c.speed = s
	return cb
}

func (cb *carBuilder) Build() Interface {
	return cb.c
}

使用

1
2
3
4
5
6
7
8
9
10
11
func main() {
	assembly := car.NewCarBuilder()

	familyCar := assembly.Wheels(car.SportWheels).TopSpeed(50 * car.MPH).Color(car.RedColor).Build()
	familyCar.Drive()
	familyCar.Stop()

	sportCar := assembly.Wheels(car.SteelWheels).TopSpeed(150 * car.MPH).Color(car.GreenColor).Build()
	sportCar.Drive()
	sportCar.Stop()
}