Go语言（十五） 反射

import (
   "fmt"
   "reflect"
)

func TestType(a interface{})  {
   //获取类型（静态信息）
   t := reflect.TypeOf(a)
   kind := t.Kind()
   switch kind {
   case reflect.Int:
      fmt.Printf("a is a int\n")
      a = 2
   case reflect.String:
      fmt.Printf("a is a string\n")
   }
   fmt.Printf("t=%v,kind=%v\n\n",t,kind)
}

func TestValue(a interface{}) {
   v := reflect.ValueOf(a)
   //kind := v.Kind()
   t := v.Type()
   switch t.Kind() {
   case reflect.Int:
      fmt.Printf("a is a int\n")
      v.SetInt(10000)
   case reflect.String:
      v.SetString("xxx")
      fmt.Printf("a is a string\n")
   case reflect.Ptr:
      t1 := v.Elem().Type()
      switch (t1.Kind()) {
      case reflect.Int:
         v.Elem().SetInt(100)
         fmt.Printf("ptn is int \n")
      case reflect.String:
         v.Elem().SetString("hello")
         fmt.Printf("ptn is string\n")
      }
      fmt.Printf("a=%v is a point type\n",t1)
   }
   fmt.Printf("v=%v,kind=%v\n\n",v,t)
}

func main() {
   //var a int
   //TestType(a)
   //fmt.Printf("a=%v\n",a)
   //var b string
   //TestType(b)
   var c int
   TestValue(&c)
   var d string
   TestValue(&d)
   fmt.Printf("c=%v, d=%v\n",c,d)
}

type Users struct {
   Name string  `json:"name"`
   Age int
   Sex string
}

//1. 获取a的类型
//2. 我要动态改变a里面存的值
//3. 如果a里面存储的是一个结构体，那可以通过反射获取结构体中的字段信息以及调用结构体里面的方法
func TestValueStruct(a interface{}) {

   v := reflect.ValueOf(a)
   t := v.Type()
   switch t.Kind()  {
   case reflect.Struct:
      fieldNum := t.NumField()
      fmt.Printf("field num:%d\n", fieldNum)
      for i := 0; i <fieldNum; i++{
         field := t.Field(i)
         vField := v.Field(i)

         fmt.Printf("field[%d] name:%s, json key:%s, val:%v\n",
            i, field.Name, field.Tag.Get("json"), vField.Interface())
      }

   }
}
func main()  {
      var user Users
      user.Name = "xxx"
      user.Age = 100
      user.Sex = "man"
      TestValueStruct(user)
      fmt.Printf("user:%#v\n", user)
}

type S struct {
   A int
   B string
}

func (s *S) Test() {
   fmt.Printf("this is a test\n")
}

func (s *S) SetA (a int) {
   s.A = a
}

func main() {
   s := S{23,"abc"}
   v := reflect.ValueOf(&s)
   m := v.MethodByName("Test")
   var args1 []reflect.Value
   m.Call(args1)
   setA := v.MethodByName("SetA")
   var args2 []reflect.Value
   args2 = append(args2,reflect.ValueOf(100))
   setA.Call(args2)   #修改结构体中的值
   fmt.Printf("s:%#v\n",s)
}

package json_reflect

import (
   "fmt"
   "reflect"
)
func Marshals(data interface{}) (jsonStr string) {

   t := reflect.TypeOf(data)
   v := reflect.ValueOf(data)
   switch t.Kind(){
   case reflect.String,reflect.Int,reflect.Int32:
      jsonStr = fmt.Sprintf("\"%v\"", data)
   case reflect.Struct:
      numField := t.NumField()
      for i := 0; i < numField; i++ {
         //类型信息
         name := t.Field(i).Name
         tag := t.Field(i).Tag.Get("json")
         if len(tag) > 0 {
            name = tag
         }
         //值信息
         vField := v.Field(i)
         vFieldValue := vField.Interface()
         //拼接json
         if t.Field(i).Type.Kind()  == reflect.String {
            jsonStr += fmt.Sprintf("\"%s\":\"%v\"", name, vFieldValue)
         } else {
            jsonStr += fmt.Sprintf("\"%s\":%v", name, vFieldValue)
         }

         if i != numField - 1 {
            jsonStr += ","
         }
      }

      jsonStr = "{" +jsonStr + "}"
   }
   return
}

package main

import (
   "fmt"
   "oldBoy/day9/json_reflect"
)

type User struct {
   Name string `json:"name"`
   Age  int    `json:"age"`
   Sex  string `json:"sex"`
}

func main() {
   var a string = "hello abc"
   jsonStr := json_reflect.Marshals(a)
   fmt.Printf(jsonStr)

   var user User
   user.Name = "aaa"
   user.Age = 10
   user.Sex = "male"

   jsonStr = json_reflect.Marshals(user)
   fmt.Printf(jsonStr)
}