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NGÀY 5 – POINTERS, STRUCTS & METHODS

date
Dec 12, 2025
slug
pointers-structs-method
status
Published
tags
Go Lang
summary
Mục tiêu: hiểu cơ chế tham chiếu/tham trị trong Go, nắm struct, method và cách chúng hoạt động với pointer receivers.
type
Post

Bài – Tạo struct Person

Yêu cầu:
  • name string
  • age int
  • city string
  • Method Hello() in ra câu: "Hi, I’m {name} from {city}"
  • Method GrowUp() tăng tuổi +1
package main

import "fmt"

type Person struct {
	name string
	age  int
	city string
}

func (p *Person) Hello() {
	fmt.Printf("Hi, I’m %s from %s\n", p.name, p.city)
}

func (p *Person) GrowUp() {
	p.age += 1
}

func main() {
	p := Person{name: "Alice", age: 20, city: "Hanoi"}
	p.Hello()
	p.GrowUp()
	fmt.Printf("%s is now %d years old.\n", p.name, p.age)
}

package main

import "fmt"

type User struct {
	ID    int
	Name  string
	Email string
	Age   int
}

func NewUser(id int, name, email string, age int) User {
	return User{
		ID:    id,
		Name:  name,
		Email: email,
		Age:   age,
	}
}

// pointer receiver to update email
func (u *User) UpdateEmail(newEmail string) {
	u.Email = newEmail
}

// value receiver for age check
func (u User) IsAdult() bool {
	return u.Age >= 18
}

func (u User) PrintInfo() {
	fmt.Printf("User Info:\n  ID: %d\n  Name: %s\n  Email: %s\n  Age: %d\n", u.ID, u.Name, u.Email, u.Age)
}

func main() {
	user := NewUser(1, "Alice", "[email protected]", 20)
	user.PrintInfo()

	fmt.Println("Is adult:", user.IsAdult())

	user.UpdateEmail("[email protected]")
	fmt.Println("After email update:")
	user.PrintInfo()
}

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