go reflect TypeOf 与ValueOf

学习go的反射对于理解go的底层实现以及接口机制有着非常重要的价值；本篇文章从一个源程序来体验一下go反射的两个核心函数TypeOf 和ValueOf的使用方法，特别体验下怎么根据type构造type实例的办法。

package mainimport ("fmt""reflect")type Speaker interface {Speak()stringSet(string)}type Teacher struct {Name string}func (this *Teacher) Speak() string {return this.Name}func (this *Teacher) Set(name string) {this.Name = name}func TestRef(s Speaker)(t reflect.Type){    reflectVal := reflect.ValueOf(s)//t = reflect.Indirect(reflectVal).Type()t = reflectVal.Elem().Type()fmt.Printf("reflect.ValueOf(%v).Elem().Type()=%v\n",s,t)return}func TestRef2(s Speaker)(t reflect.Type){    //t = reflect.TypeOf(s).Elem()//fmt.Printf("reflect.TypeOf(%v).Elem()=%v\n",s,t)    t = reflect.TypeOf(s)fmt.Printf("reflect.TypeOf(%v)=%v\n",s,t)return}func TestRef3(s *Teacher)(t reflect.Type){    t = reflect.TypeOf(s).Elem()fmt.Printf("reflect.TypeOf(%v).Elem()=%v\n",s,t)return}func main(){te := &Teacher{Name:"newyear",}fmt.Printf("source=%v\n",te)fmt.Printf("\n")var tea Speaker = te t1 := TestRef(tea)//默认是创建一个零值实例，string 就是""if m, ok := reflect.New(t1).Interface().(Speaker); ok {fmt.Printf("reflect.New(%v).Interface().(Speaker)=%v\n",t1, m)fmt.Printf("se.Speak()=%v\n",m.Speak())m.Set("2014")fmt.Printf("reflect.New(%v).Interface().(Speaker)=%v\n",t1, m)fmt.Printf("se.Speak()=%v\n",m.Speak())}fmt.Printf("Source Instance te=%v\n",te)fmt.Printf("\n")t2 := TestRef2(tea)//if m, ok := reflect.New(t2).Interface().(Speaker); ok {if m, ok := reflect.New(t2.Elem()).Interface().(Speaker); ok {fmt.Printf("reflect.New(%v.Elem()).Interface().(Speaker)=%v\n",t2, m)fmt.Printf("se.Speak()=%v\n",m.Speak())    m.Set("2015")fmt.Printf("reflect.New(%v.Elem()).Interface().(Speaker)=%v\n",t2, m)fmt.Printf("se.Speak()=%v\n",m.Speak())}fmt.Printf("Source Instance te=%v\n",te)fmt.Printf("\n")t3 := TestRef3(te)if m, ok := reflect.New(t3).Interface().(Speaker); ok {fmt.Printf("reflect.New(%v).Interface().(Speaker)=%v\n", t3, m)fmt.Printf("se.Speak()=%v\n",m.Speak())m.Set("2016")fmt.Printf("reflect.New(%v).Interface().(Speaker)=%v\n", t3, m)fmt.Printf("se.Speak()=%v\n",m.Speak())}fmt.Printf("Source Instance te=%v\n",te)fmt.Printf("\n")fmt.Printf("reflect.TypeOf(tea)=%v\n",reflect.TypeOf(tea))fmt.Printf("reflect.TypeOf(tea).Elem()=%v\n",reflect.TypeOf(tea).Elem())fmt.Printf("reflect.ValueOf(tea)=%v\n",reflect.ValueOf(tea))fmt.Printf("reflect.ValueOf(tea).Elem()=%v\n",reflect.ValueOf(tea).Elem())fmt.Printf("\n")   if se, ok := reflect.ValueOf(tea).Interface().(Speaker); ok {   //if se, ok := reflect.ValueOf(te).Interface().(Speaker); ok {fmt.Printf("reflect.ValueOf(%v).Interface().(Speaker)=%v\n",tea, se)fmt.Printf("se.Speak()=%v\n",se.Speak())se.Set("2017")fmt.Printf("reflect.ValueOf(%v).Interface().(Speaker)=%v\n",tea, se)fmt.Printf("se.Speak()=%v\n",se.Speak())   }fmt.Printf("Source Instance te=%v\n",te)fmt.Printf("\n")   //if se, ok := reflect.New(reflect.TypeOf(te).Elem()).Interface().(Speaker); ok {   if se, ok := reflect.New(reflect.TypeOf(tea).Elem()).Interface().(Speaker); ok {fmt.Printf("reflect.New(reflect.TypeOf(%v).Elem()).Interface().(Speaker)=%v\n",tea,se)fmt.Printf("se.Speak()=%v\n",se.Speak())se.Set("2018")fmt.Printf("reflect.New(reflect.TypeOf(%v).Elem()).Interface().(Speaker)=%v\n",tea,se)fmt.Printf("se.Speak()=%v\n",se.Speak())   }fmt.Printf("Source Instance te=%v\n",te)fmt.Printf("\n") if se, ok := reflect.New(reflect.TypeOf(te).Elem()).Interface().(Speaker); ok {fmt.Printf("reflect.New(reflect.TypeOf(%v).Elem()).Interface().(Speaker)=%v\n",te,se)fmt.Printf("se.Speak()=%v\n",se.Speak())se.Set("2019")fmt.Printf("se.Speak()=%v\n",se.Speak())fmt.Printf("reflect.New(reflect.TypeOf(%v).Elem()).Interface().(Speaker)=%v\n",te,se)   }fmt.Printf("Source Instance te=%v\n",te)fmt.Printf("\n")}