alter_reflect.go

package main

import (
	"fmt"
	"reflect"
)

type User struct {
	ID    int
	Email string `json:"email" yaml:"email_address"`
	Data  struct {
		Key   string
		Value bool
	}
}

func main() {
	user := User{ID: 42}
	aString := "This is a string variable"

	// getting the reflect values for user and aString
	reflectedUserValue := reflect.ValueOf(user)
	reflectedStringValue := reflect.ValueOf(aString)

	fmt.Println(reflectedUserValue.Interface())
	fmt.Println(reflectedStringValue.Interface())
	fmt.Println("-------------------------------------")

	//getting the reflect pointers to be able to modify the values
	reflUserPtr := reflect.ValueOf(&user)
	reflStrinPtr := reflect.ValueOf(&aString)

	secondUser := User{ID: 54, Email: "new@value.com"}
	secondUserValue := reflect.ValueOf(secondUser)
	reflUserPtr.Elem().Set(secondUserValue)

	reflStrinPtr.Elem().SetString("Updated value")

	// values are  modified
	fmt.Println(user)
	fmt.Println(aString)

	fmt.Println("-------------------------------------")
	// creating a new User instance using reflection
	rType := reflect.TypeOf(user)
	newUserValue := reflect.New(rType)
	newUserValue.Elem().Field(0).SetInt(66)
	newUserValue.Elem().Field(1).SetString("iamnew@example.com")

	// cast the reflected value to the User type
	newUser := newUserValue.Interface().(*User)
	fmt.Println("New user fields: ", newUser.ID, newUser.Email)
}