Example (Go) - Structs

// go.mod
module example.com/structs

go 1.22.0

// structs.go
package main

import (
	"fmt"

	"example.com/structs/user"
)


func main() {
	firstName := getUserData("Please enter your first name: ")
	lastName := getUserData("Please enter your last name: ")
	birthDate := getUserData("Please enter your birthdate (MM/DD/YYYY): ")

	// var appUser User = User{firstName, lastName, birthDate, time.Now()}
	// appUser := User{firstName, lastName, birthdate, time.Now()}
	// appUser = User{
	//     firstName: firstName,
	//     lastName: lastName,
	//     birthdate: birthdate,
	//     createdAt: time.Now(),
	// }
	// var appUser User = newUser(firstName, lastName, birthDate)
	// var appUser *User = newUser(firstName, lastName, birthDate)
	// appUser, err := newUser(firstName, lastName, birthDate)
	appUser, err := user.New(firstName, lastName, birthDate)

    if err != nil {
        panic(err)
    }

    admin := user.NewAdmin("test@example.come", "admin")
    // ====If you use anonymous embedding, you can access the fields and methods directly====
    // admin.User.OutputUserDetail()
    admin.OutputUserDetail()
    admin.ClearUserName()
    admin.OutputUserDetail()

	// fmt.Println(appUser)
	// outputUserDetail(&appUser)
	appUser.OutputUserDetail()
	appUser.ClearUserName()
	appUser.OutputUserDetail()
}

// func outputUserDetail(user *User) {
//     // ====Standard method is as follow. But Go has shortcut so can access the====
//     // ====fields directly====
//
//     // fmt.Println((*user).firstName, (*user).lastName, (*user).birthDate)
//     fmt.Println(user.firstName, user.lastName, user.birthDate)
// }

func getUserData(promptText string) string {
	fmt.Print(promptText)
	var value string
    // ====Scanln runs until carriage return hit====
	fmt.Scanln(&value)
	return value
}

// user/user.go
package user

import (
	"errors"
	"fmt"
	"time"
)

type User struct {
	firstName string
	lastName  string
	birthDate string
	createdAt time.Time
}

type Admin struct {
    email string
    password string
    // user User
    // ====or call anonymously====
    User
}

func NewAdmin(email, password string) Admin {
    return Admin{
        email: email,
        password: password,
        User: User{
            firstName: "ADMIN",
            lastName: "ADMIN",
            birthDate: "---",
            createdAt: time.Now(),
        },
    }
}

// ====Creating struct methods====
// func (user User) outputUserDetail() {
func (user User) OutputUserDetail() {
	// ====the (user User) above is a "Receiver" argument====
	fmt.Println(user.firstName, user.lastName, user.birthDate)
}

// ====Function that changes data in a struct====
// ====it needs to take in the receiver as a pointer====
//
//	func (user User) clearUserName() {
//	    user.firstName = ""
//	    user.lastName = ""
//	}
// func (user *User) clearUserName() {
func (user *User) ClearUserName() {
	user.firstName = ""
	user.lastName = ""
}

// ====Creator or Constructor aren't feature of go====
// ====just a convention====
//
//	func newUser(firstName, lastName, birthDate string) User {
//		return User{
//	        firstName: firstName,
//	        lastName:  lastName,
//	        birthDate: birthDate,
//	        createdAt: time.Now(),
//	    }
//	}
// func newUser(firstName, lastName, birthDate string) (*User, error) {
// func NewUser(firstName, lastName, birthDate string) (*User, error) {
func New(firstName, lastName, birthDate string) (*User, error) {
	if firstName == "" || lastName == "" || birthDate == "" {
		return nil, errors.New("First Name, Last Name and Birth Date are required")
	}

	return &User{
		firstName: firstName,
		lastName:  lastName,
		birthDate: birthDate,
		createdAt: time.Now(),
	}, nil
}