go装饰器

普通装饰器（go中没有python的@语法糖）

package main

import "fmt"

func user_logging(fun func()) func() func() {
    wrapper := func() func(){
        fmt.Println("this func is", fun)
        fmt.Println("the end of foo")
        return fun
    }
    return wrapper
}

func foo()  {
    println("i am foo")
}

func main() {
    foo := user_logging(foo)
    fmt.Println(foo())
}

//this func is 0x490840
//the end of foo
//0x490840

package main

import "fmt"

func user_logging(fun func()) func() { // 装饰器函数
   wrapper := func() {
      fmt.Println("this func is", fun)
      fun()
      fmt.Println("the end of foo")
   }
   return wrapper
}

func foo()  {
   println("i am foo")
}

func main() {
   foo := user_logging(foo)
   foo()
}

//this func is 0x490840
//i am foo
//the end of foo

功能函数加参数

package main

import (
    "fmt"
    "time"
)

func show_time(fun func(...int)) func(...int) { // 装饰器函数
    wrapper := func(args ...int) {
        start := time.Now().Unix()
        fun(args...)
        end := time.Now().Unix()
        fmt.Println(start, end)
        fmt.Printf("spend %d", end - start)
    }
    return wrapper
}

func add(args ...int)  {    // 功能函数
    sums := 0
    for _, v := range args {
        sums += v
    }
    fmt.Println(sums)
    time.Sleep(3 * time.Second)
}

func main() {
    add := show_time(add)
    add(1, 2, 3, 4, 5)
}

装饰器函数加参数

package main

import (
    "fmt"
    "time"
)

func logger(flag bool) func(fun func(...int)) func(...int) {
    show_time := func(fun func(...int)) func(...int) { // 装饰器函数
        wrapper := func(args ...int) {
            start := time.Now().Unix()
            fun(args...)
            end := time.Now().Unix()
            fmt.Println(start, end)
            fmt.Printf("spend %d\n", end - start)
            if flag == true {
                fmt.Println("日志记录")
            }
        }
        return wrapper
    }
    return show_time
}


func add(args ...int)  {    // 功能函数
    sums := 0
    for _, v := range args {
        sums += v
    }
    fmt.Println(sums)
    time.Sleep(3 * time.Second)
}

func test() {
    show_time := logger(false)
    add := show_time(add)
    add(1, 2, 3, 4, 5)
}

func main() {
    show_time := logger(true)
    add := show_time(add)
    add(1, 2, 3, 4, 5)

    test()
}
//15
//1554351453 1554351456
//spend 3
//日志记录

//15
//1554351456 1554351459
//spend 3

通过反射实现的通用型装饰器

package main

import (
   "fmt"
   "reflect"
)

func Decorator(decoPtr, fn interface{}) (err error) {
   var decoratedFunc, targetFunc reflect.Value

   decoratedFunc = reflect.ValueOf(decoPtr).Elem()
   targetFunc = reflect.ValueOf(fn)

   v := reflect.MakeFunc(targetFunc.Type(),
      func(in []reflect.Value) (out []reflect.Value) {
         fmt.Println("before")
         args := []reflect.Value{}
         if len(in) == 1 && in[0].Kind() == reflect.Slice {
            for i := 0; i < in[0].Len(); i++ {
               args = append(args, in[0].Index(i))
            }
            in = args
         }
         out = targetFunc.Call(in)
         fmt.Println("after")
         return
      })

   decoratedFunc.Set(v)
   return
}

func foo(a, b, c int) int {
   fmt.Println(a)
   return b
}


func main() {
   myfoo := foo
   Decorator(&myfoo, foo)
   myfoo(1, 2, 3)
}

//before
//1
//after