package main

import (
    "fmt"
    "reflect"
)

func main() {
    var x int = 42
    t := reflect.TypeOf(x)      // 類型信息
    v := reflect.ValueOf(x)     // 值信息

    fmt.Println("Type:", t)           // int
    fmt.Println("Value:", v)          // 42
    fmt.Println("Kind:", v.Kind())    // int
}

type Person struct {
    Name string `json:"name"`
    Age  int    `json:"age"`
}

func inspectStruct(s interface{}) {
    v := reflect.ValueOf(s).Elem()
    t := v.Type()

    for i := 0; i < v.NumField(); i++ {
        field := v.Field(i)
        structField := t.Field(i)
        tag := structField.Tag.Get("json")

        fmt.Printf("Field: %s, Value: %v, Tag: %s\n",
            structField.Name, field.Interface(), tag)
    }
}

func main() {
    p := &Person{Name: "Alice", Age: 30}
    inspectStruct(p)
}

Field: Name, Value: Alice, Tag: name
Field: Age, Value: 30, Tag: age

func setAge(obj interface{}, newAge int) {
    v := reflect.ValueOf(obj).Elem()
    ageField := v.FieldByName("Age")
    if ageField.CanSet() {
        ageField.SetInt(int64(newAge))
    }
}

func main() {
    p := &Person{Name: "Bob", Age: 25}
    setAge(p, 35)
    fmt.Println(*p) // {Bob 35}
}

func (p Person) Greet() {
    fmt.Printf("Hello, I'm %s, %d years old.\n", p.Name, p.Age)
}

func callMethod(obj interface{}, methodName string) {
    v := reflect.ValueOf(obj)
    method := v.MethodByName(methodName)
    if method.IsValid() {
        method.Call(nil) // 無參數(shù)調(diào)用
    }
}

func main() {
    p := &Person{Name: "Charlie", Age: 28}
    callMethod(p, "Greet") // 輸出問候語
}