add reflect decorator

Author: pibigstar

design/decorator/decorator_func.go

@@ -1,7 +1,9 @@
 package decorator
 
 import (
+	"fmt"
 	"net/http"
+	"reflect"
 )
 
 // 方法的装饰器模式, 包装某个方法
@@ -21,3 +23,33 @@ func Auth(h http.HandlerFunc) http.HandlerFunc {
 func f(w http.ResponseWriter, r *http.Request) {
 	w.Write([]byte("Hello World"))
 }
+
+// 用 reflection 机制写的一个比较通用的修饰器
+// https://coolshell.cn/articles/17929.html
+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")
+			out = targetFunc.Call(in)
+			fmt.Println("after")
+			return
+		})
+
+	decoratedFunc.Set(v)
+	return
+}
+
+func foo(a, b, c int) int {
+	fmt.Printf("%d, %d, %d \n", a, b, c)
+	return a + b + c
+}
+
+func bar(a, b string) string {
+	fmt.Printf("%s, %s \n", a, b)
+	return a + b
+}

design/decorator/decorator_func_test.go

@@ -16,3 +16,14 @@ func TestAuth(t *testing.T) {
 		t.Error(err)
 	}
 }
+
+func TestReflectDecorator(t *testing.T) {
+	type MyFoo func(int, int, int) int
+	var myfoo MyFoo
+	Decorator(&myfoo, foo)
+	myfoo(1, 2, 3)
+
+	mybar := bar
+	Decorator(&mybar, bar)
+	mybar("hello", "world!")
+}