Go language basic reflection reflect

Reflection reflect
struct
reflect.TypeOf(i interface{})-->Type
gets the type and field name of the field of the structure

the type of the method, the name of the method

package main

import (
   "fmt"
   "reflect"
)

type Person struct {
   Name string
   Age int
   Sex string
}

func (p Person)Say(msg string)  {
   fmt.Println("hello，",msg)
}
func (p Person)PrintInfo()  {
   fmt.Printf( "Name: %s, Age: %d, Gender: %s\n" , p.Name , p.Age , p.Sex)
}

func main () {
    //1. Create a struct object
    p1 := Person{ "Wang Ergou" , 30 , "Male" }
    //1. Part 1: Manipulate the fields in the structure through reflection: get the fields of the fields Type, name, value. .
   //Get the type of p1 through TypeOf() under the reflect package
 t1:=reflect.TypeOf(p1)
   
   fmt.Println(t1) //main.Person
    fmt.Println(t1.Name()) //Person
    fmt.Println(t1.Kind()) //struct
    //Get the value of p1 through ValueOf() in the reflect package Value
    v1:=reflect.ValueOf(p1) //{Wang Ergou 30 male}
    fmt.Println(v1)

   //Detailed operation: determine the type of t1 is the structure type
 if t1.Kind() == reflect. Struct {
       //Get the number of fields
 count:=t1.NumField() //3 fields
 fmt.Println(count)               

      for i:=0;i<count;i++{
         filed:=t1.Field(i)
         val:=v1.Field(i).Interface() //Get the value of the corresponding field according to v1, ---> empty interface type
 //fmt.Println(filed          )
          fmt.Println( "Field name:" , filed. Name , "Field Type:" , filed.Type , "Field Value:" , val)
      }
   }


   //2. Through reflection, the operation method
    fmt.Println(t1.NumMethod())
    for i:= 0 ; i<t1.NumMethod() ; i++{
      method:=t1.Method(i)
      fmt.Println(method.Name,method.Type)
   }

   //Execute method
    m1:=v1.MethodByName( "PrintInfo" )
   m1.Call(nil) //Execute PrintInfo() corresponding to m1
 m2:=v1.MethodByName( "Say" )
   
   m2.Call([]reflect.Value{reflect.ValueOf( "Hello " )}) // string-->Value

 }

reflect.ValueOf(i interface{})-->Value
gets the value of the field of the structure

Get the object of the method--->Call(), execute the corresponding method

package main

import (
   "reflect"
   "fmt"
)

type Animal struct {
   Name string
   Age  int
}

type Cat struct {
   Animal
   Color string
}

func main() {
   c1 := Cat{Animal{"猫咪", 1}, "白色"}

   t1 := reflect.TypeOf(c1)
   fmt.Println(t1.NumField())

   for i := 0; i < t1.NumField(); i++ {
      field := t1.Field(i)
      fmt.Println(field)
   }

   //获取匿名字段
   /*
   匿名字段，可以通过下标获取
   FieldByIndex（[]int{0}）-->Animal
   FieldByIndex（[]int{0,0}）-->Animal中的第一个字段：Name
    */
   f1:=t1.FieldByIndex([]int{0,0})
   fmt.Println(f1.Name,f1.Type)//Name string
   f2:=t1.FieldByIndex([]int{0,1})
   fmt.Println(f2.Name,f2.Type)


   v1:=reflect.ValueOf(c1)

   name:=v1.FieldByIndex([]int{0,0})
   fmt.Println(name)
}

//Anonymous field
t1.FieldByIndex([]int{0,0})
v1.FieldByIndex([]int{0,0})
//Change data
reflect.ValueOf(p1)-->value
reflect.Struct
reflect.ValueOf (&p1)-->value
reflect.Ptr
v1 = v1.Elem()
CanSet()-->bool
c1.FieldByName()-->f1

f1.SetXXX(新value)

package main

import (
   "reflect"
   "fmt"
)

type Student struct {
   Name string
   Age int
   School string
}
func main()  {
   /*
   通过反射，来更改对象的数值：前提是数据可以被更改
    */
    s1:=Student{"王二狗",19,"新东方"}
    fmt.Printf("%T\n",s1) //main.Student
    p1:=&s1
    fmt.Printf("%T\n",p1) //*main.Student
    fmt.Println(s1.Name)
    fmt.Println((*p1).Name,p1.Name)


    v1:= reflect.ValueOf(&s1) // value

    if v1.Kind()==reflect.Ptr{
      fmt.Println(v1.Elem().CanSet())
      v1 = v1.Elem()
    }

    f1:=v1.FieldByName("Name")
    f1.SetString("王三狗")
    f3:=v1.FieldByName("School")
    f3.SetString("蓝翔学校")
    fmt.Println(s1)




}