Golang如何使用装饰器模式动态增加功能

<pre class="brush:php;toolbar:false;">type HandlerFunc func(string) string

<pre class="brush:php;toolbar:false;">func LoggingDecorator(h HandlerFunc) HandlerFunc {
    return func(s string) string {
        fmt.Printf("调用前: 参数=%s\n", s)
        result := h(s)
        fmt.Printf("调用后: 返回=%s\n", result)
        return result
    }
}

<pre class="brush:php;toolbar:false;">func TimingDecorator(h HandlerFunc) HandlerFunc {
    return func(s string) string {
        start := time.Now()
        result := h(s)
        fmt.Printf("耗时: %v\n", time.Since(start))
        return result
    }
}

<pre class="brush:php;toolbar:false;">var handler HandlerFunc = func(s string) string {
    time.Sleep(100 * time.Millisecond)
    return "Hello, " + s
}
<p>// 装饰两层
decorated := LoggingDecorator(TimingDecorator(handler))</p><p>// 调用
result := decorated("World")
fmt.Println(result)</p>

<pre class="brush:php;toolbar:false;">func AuthDecorator(h http.HandlerFunc) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        token := r.Header.Get("Authorization")
        if token == "" {
            http.Error(w, "未授权", http.StatusUnauthorized)
            return
        }
        h(w, r)
    }
}

<pre class="brush:php;toolbar:false;">http.HandleFunc("/api/data", AuthDecorator(dataHandler))