go 的装饰器模式

和 Python 一样，函数作为一等公民的语言来说，实现装饰器都比较方便。

func help(name string) {
    fmt.Println(fmt.Sprintf("help %s", name))
}

func decorator(a func(name string)) func(string) {
    return func(name string) {
        fmt.Println("decorator code before")
        a(name)
        fmt.Println("decorator code after")
    }
}

func main() {
    decoratorFunc := decorator(help)
    decoratorFunc("go")
}

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如果有多个装饰器函数，那么可以：

type Func func(string)
type Decorator func(Func) Func

func decoratorsHandler(h Func, decors ...Decorator) Func {
    cnt := len(decors)
    for i := range decors {
        d := decors[cnt-1-i]
        h = d(h)
    }

    return h
}

func decorator1(a Func) Func {
    return func(name string) {
        fmt.Println("decorator code1")
        a(name)
    }
}

func decorator2(a Func) Func {
    return func(name string) {
        fmt.Println("decorator code2")
        a(name)
    }
}

func help(name string) {
    fmt.Println(fmt.Sprintf("help %s", name))
}

func main() {
    decoratorsFunc := decoratorsHandler(help, decorator1, decorator2)
    decoratorsFunc("go")
}

image.png