装饰模式使用对象组合的方式动态改变或增加对象行为。
Go语言借助于匿名组合和非入侵式接口可以很方便实现装饰模式。
使用匿名组合，在装饰器中不必显式定义转调原对象方法。
decorator.go
package decorator
type Component interface {
Calc() int
}
type ConcreteComponent struct{}
func (*ConcreteComponent) Calc() int {
return 0
}
type MulDecorator struct {
Component
num int
}
func WarpMulDecorator(c Component, num int) Component {
return &MulDecorator{
Component: c,
num: num,
}
}
func (d *MulDecorator) Calc() int {
return d.Component.Calc() * d.num
}
type AddDecorator struct {
Component
num int
}
func WarpAddDecorator(c Component, num int) Component {
return &AddDecorator{
Component: c,
num: num,
}
}
func (d *AddDecorator) Calc() int {
return d.Component.Calc() + d.num
}
decorator_test.go
package decorator
import "fmt"
func ExampleDecorator() {
var c Component = &ConcreteComponent{}
c = WarpAddDecorator(c, 10)
c = WarpMulDecorator(c, 8)
res := c.Calc()
fmt.Printf("res %d\n", res)
// Output:
// res 80
}