工厂方法模式
<p>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。</p>
<p>Go中不存在继承 所以使用匿名组合来实现</p>
<h4>factorymethod.go</h4>
<pre><code>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 &amp;PlusOperator{
OperatorBase: &amp;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 &amp;MinusOperator{
OperatorBase: &amp;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
}</code></pre>
<h4>factorymethod_test.go</h4>
<pre><code>package factorymethod
import &quot;testing&quot;
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(&quot;error with factory method pattern&quot;)
}
factory = MinusOperatorFactory{}
if compute(factory, 4, 2) != 2 {
t.Fatal(&quot;error with factory method pattern&quot;)
}
}</code></pre>