Factory pattern

The Factory Pattern is a creational design pattern that provides an interface for creating objects in a superclass but allows subclasses to alter the type of objects that will be created. It helps in promoting loose coupling by reducing the need to bind application-specific classes into the code.

Benefits of the Factory Pattern

• Encapsulation: The creation logic is encapsulated in the factory function, making the code easier to maintain and extend.
• Flexibility: It provides flexibility in object creation. If the creation logic changes, only the factory function needs to be updated, not the entire codebase.
• Decoupling: It promotes loose coupling by reducing dependencies between components.

package main

import (
	"fmt"
	"time"

	"github.com/google/uuid"
)

// User is the type for all user accounts.
type User struct {
	ID       string
	Username string
	Email    string
	JoinedAt time.Time
	Status   string
}

// NewUser is the factory function that creates a new User instance with sensible defaults.
func NewUser(username, email string) *User {
	return &User{
		ID:       uuid.New().String(),
		Username: username,
		Email:    email,
		JoinedAt: time.Now(),
		Status:   "active", // default status
	}
}

func main() {
	// Use the factory function to create new Users.
	user1 := NewUser("john_doe", "[email protected]")
	user2 := NewUser("jane_smith", "[email protected]")

	// Print out the results in a nicely formatted way.
	printUser(user1)
	printUser(user2)
}

// printUser prints the details of a User in a nicely formatted way.
func printUser(user *User) {
	fmt.Printf("User Details:\n")
	fmt.Printf("ID:        %s\n", user.ID)
	fmt.Printf("Username:  %s\n", user.Username)
	fmt.Printf("Email:     %s\n", user.Email)
	fmt.Printf("JoinedAt:  %s\n", user.JoinedAt.Format(time.RFC1123))
	fmt.Printf("Status:    %s\n", user.Status)
	fmt.Println("----------------------------")
}

Output

~ go run main.go

User Details:
ID:        89019289-69bc-4154-91a1-62332a884ea3
Username:  john_doe
Email:     [email protected]
JoinedAt:  Sun, 30 Jun 2024 12:34:15 +04
Status:    active
----------------------------

User Details:
ID:        9a9c71b2-dfb4-4568-a492-e3f0c75cf2b8
Username:  jane_smith
Email:     [email protected]
JoinedAt:  Sun, 30 Jun 2024 12:34:15 +04
Status:    active
----------------------------
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