Go言語の基本的な反射の例について説明する

func TypeOf(i interface{}) Type //Type is an alias for interface{}

reflect.TypeOf(10) //int
reflect.TypeOf(struct{ age int }{10}) //struct { age int }

reflect.TypeOf(struct{ age int }{10}).Kind() //reflect.Struct
reflect.ValueOf("hello word").Kind() //reflect.String

func ValueOf(i interface{}) Value //value is a struct {} alias

reflect.ValueOf("hello word") //hello word
reflect.ValueOf(struct{ age int }{10}) //{10}

str := "hello word"
reflect.ValueOf(&str).Elem().SetString("Zhang San")

// first step: ValueOf(): pass in the address of a variable, return is the address of the variable Elem(): return is the original value of the variable
Elem:=reflect.ValueOf(& variable name).Elem()
// Second step FieldByName(): pass in the name of the structure field SetString(): pass in the value of the variable you want to modify
elem.FieldByName("Name").SetString("李四")

// Define a User struct
type User struct {
	Name string
	Age int
Age int }
user := User{Name: "Zhang San", Age: 10}
//Elem() gets the original value of user
Elem := reflect.ValueOf(&user).Elem()
//FieldByName() Returns the structure field with the given name by Name Modifies the original value by SetString
elem.FieldByName("Name").SetString("李四")
elem.FieldByName("Age").SetInt(18)

//MethodByName(): pass the method name, which must be large or small Call(): the formal reference to the method
reflect.ValueOf(variableName).MethodByName(methodName).Call([]reflect.Value{})
reflect.ValueOf(variableName).MethodByName(methodName).Call(make([]reflect.Value, 0))

type User struct {
	Name string `json:"name" name:"Zhang San"`
	Age int
Age int }
func (_ User) Say() {
	fmt.Println("user Say")
}
user := User{Name: "Zhang San", Age: 10}
reflect.ValueOf(&user).MethodByName("Say").Call([]reflect.Value{})
  reflect.ValueOf(user).MethodByName("Say").Call(make([]reflect.Value, 0))

reflect.ValueOf(variableName).MethodByName(methodName).Call([]reflect.Value{reflect.ValueOf("It's time to talk"), reflect.ValueOf(1)})

type User struct {
  Name string `json:"name" name:"Zhang San"`
  Age int
Age int }
func (_ User) Say() {
  fmt.Println("user Say")
}
user := User{Name: "Zhang San", Age: 10}
reflect.ValueOf(user).MethodByName("SayContent").Call([]reflect.Value{reflect.ValueOf("Time to talk"), reflect.ValueOf( 1)})

package main
import (
	"fmt"
	"reflect"
)
func main() {
	//1. Get the type of the variable
	fmt.Println("Get variable type")
	fmt.Println(reflect.TypeOf(10)) //int
	fmt.Println(reflect.TypeOf(10.0)) //float64
	fmt.Println(reflect.TypeOf(struct{ age int }{10})) //struct { age int }
	fmt.Println(reflect.TypeOf(map[string]string{ "a": "a"})) //map[string]string
	fmt.Println("")
	//2. Get the value of the variable
	fmt.Println("Get the value of the variable")
	fmt.Println(reflect.ValueOf("hello word")) //hello word
	fmt.Println(reflect.ValueOf(struct{ age int }{10})) //{10}
	fmt.Println(reflect.TypeOf(struct{ age int }{10}).Kind()) //struct
	//type determination
	if t := reflect.TypeOf(struct{ age int }{10}).Kind(); t == reflect.Struct {
		fmt.Println("is structure")
	} else {
		fmt.Println("Not a structure")
	}
	// Modify the target object
	str := "hello word"
	//Ordinary variable modification
	reflect.ValueOf(&str).Elem().SetString("Zhang San")
	fmt.Println(str)
	// structure variable modification
	user := User{Name: "Zhang San", Age: 10}
	//Elem() gets the original value of user
	Elem := reflect.ValueOf(&user).Elem()
	//FieldByName() Returns the structure field with the given name by Name Modifies the original value by SetString
	elem.FieldByName("Name").SetString("李四")
	elem.FieldByName("Age").SetInt(18)
	fmt.Println(user)
	//Get the value of the label of the structure
	fmt.Println(reflect.TypeOf(&user).Elem().Field(0).Tag.Get("name"))
	// call the parameterless method
	reflect.ValueOf(&user).MethodByName("Say").Call([]reflect.Value{})
	Reflect.ValueOf(user).MethodByName("Say").Call(make([]reflect.Value, 0))
	// call the method with reference
	reflect.ValueOf(user).MethodByName("SayContent").Call([]reflect.Value{reflect.ValueOf("Time to talk"), reflect.ValueOf( 1)})
	// Call the local method
	reflect.ValueOf(Hello).Call([]reflect.Value{})
	reflect.ValueOf(Hello).Call(nil)
	fmt.Printf("%#v\n", reflect.TypeOf(user).Field(0))
}
func Hello() {
	fmt.Println("hello")
}
type Person struct {
	Name string
name string }
type User struct {
	Person // // Reflection will treat the anonymous field as a separate field
	Name string `json:"name" name:"Zhang San"`
	Age int
}
func (_ User) Say() {
	fmt.Println("user Say")
}
func (_ User) SayContent(content string, a int) {
	fmt.Println("user", content, a)
}