工厂方法模式使用子类的方式延迟生成对象到子类中实现。

Go中不存在继承 所以使用匿名组合来实现

代码实现

package factorymethod
//Operator 是被封装的实际类接口
type Operator interface {
	SetA(int)
	SetB(int)
	Result() int
}
//OperatorFactory 是工厂接口
type OperatorFactory interface {
	Create() Operator
}
//OperatorBase 是Operator 接口实现的基类，封装公用方法
type OperatorBase struct {
	a, b int
}
//SetA 设置 A
func (o *OperatorBase) SetA(a int) {
	o.a = a
}
//SetB 设置 B
func (o *OperatorBase) SetB(b int) {
	o.b = b
}
//PlusOperatorFactory 是 PlusOperator 的工厂类
type PlusOperatorFactory struct{}
func (PlusOperatorFactory) Create() Operator {
	return &PlusOperator{
		OperatorBase: &OperatorBase{},
	}
}
//PlusOperator Operator 的实际加法实现
type PlusOperator struct {
	*OperatorBase
}
//Result 获取结果
func (o PlusOperator) Result() int {
	return o.a + o.b
}
//MinusOperatorFactory 是 MinusOperator 的工厂类
type MinusOperatorFactory struct{}
func (MinusOperatorFactory) Create() Operator {
	return &MinusOperator{
		OperatorBase: &OperatorBase{},
	}
}
//MinusOperator Operator 的实际减法实现
type MinusOperator struct {
	*OperatorBase
}
//Result 获取结果
func (o MinusOperator) Result() int {
	return o.a - o.b
}

单元测试

package factorymethod
import "testing"
func compute(factory OperatorFactory, a, b int) int {
	op := factory.Create()
	op.SetA(a)
	op.SetB(b)
	return op.Result()
}
func TestOperator(t *testing.T) {
	var (
		factory OperatorFactory
	)
	factory = PlusOperatorFactory{}
	if compute(factory, 1, 2) != 3 {
		t.Fatal("error with factory method pattern")
	}
	factory = MinusOperatorFactory{}
	if compute(factory, 4, 2) != 2 {
		t.Fatal("error with factory method pattern")
	}
}

测试结果