建造者模式（Builder Pattern）使用多个简单的对象一步一步构建成一个复杂的对象。这种类型的设计模式属于创建型模式，它提供了一种创建对象的最佳方式。

一个 Builder 类会一步一步构造最终的对象。该 Builder 类是独立于其他对象的。

代码实现

package builder

//Builder 是生成器接口
type Builder interface {
	Part1()
	Part2()
	Part3()
}

type Director struct {
	builder Builder
}

// NewDirector ...
func NewDirector(builder Builder) *Director {
	return &Director{
		builder: builder,
	}
}

//Construct Product
func (d *Director) Construct() {
	d.builder.Part1()
	d.builder.Part2()
	d.builder.Part3()
}

type Builder1 struct {
	result string
}

func (b *Builder1) Part1() {
	b.result += "1"
}

func (b *Builder1) Part2() {
	b.result += "2"
}

func (b *Builder1) Part3() {
	b.result += "3"
}

func (b *Builder1) GetResult() string {
	return b.result
}

type Builder2 struct {
	result int
}

func (b *Builder2) Part1() {
	b.result += 1
}

func (b *Builder2) Part2() {
	b.result += 2
}

func (b *Builder2) Part3() {
	b.result += 3
}

func (b *Builder2) GetResult() int {
	return b.result
}

单元测试

package builder

import "testing"

func TestBuilder1(t *testing.T) {
	builder := &Builder1{}
	director := NewDirector(builder)
	director.Construct()
	res := builder.GetResult()
	if res != "123" {
		t.Fatalf("Builder1 fail expect 123 acture %s", res)
	}
}

func TestBuilder2(t *testing.T) {
	builder := &Builder2{}
	director := NewDirector(builder)
	director.Construct()
	res := builder.GetResult()
	if res != 6 {
		t.Fatalf("Builder2 fail expect 6 acture %d", res)
	}
}