Goでファクトリを実装（「ドメイン駆動設計入門」Chapter9）

.
├── Makefile
├── README.md
├── db-migration.sh
├── docker
│   ├── go
│   │   └── Dockerfile
│   └── postgres
│       └── Dockerfile
├── docker-compose.yml
├── domain
│   └── model
│       └── user
│           ├── user.go
│           ├── user_test.go
│           ├── userapplicationservice.go
│           ├── userapplicationservice_test.go
│           ├── userfactory.go
│           ├── userfactory_test.go
│           ├── userid.go
│           ├── userid_test.go
│           ├── username.go
│           ├── username_test.go
│           ├── userrepository.go
│           ├── userrepository_test.go
│           ├── userservice.go
│           └── userservice_test.go
├── go.mod
├── go.sum
├── main.go
└── migrations
    ├── 000001_user.down.sql
    └── 000001_user.up.sql

7 directories, 25 files

package user

import (
	"github.com/google/uuid"
)

type UserFactorier interface {
	Create(UserName) (*User, error)
}

type UserFactory struct{}

func NewUserFactory() (*UserFactory, error) {
	return &UserFactory{}, nil
}

func (uf *UserFactory) Create(name UserName) (*User, error) {
	// uuidの生成が複雑な処理だと仮定
	uuidV4, err := uuid.NewRandom()
	if err != nil {
		return nil, err
	}

	userId, err := NewUserId(uuidV4.String())
	if err != nil {
		return nil, err
	}

	user, err := NewUser(*userId, name)
	if err != nil {
		return nil, err
	}
	return user, nil
}

package user

import (
	"fmt"
	"log"
)

type UserApplicationService struct {
	userFactory    UserFactorier
	userRepository UserRepositorier
	userService    UserService
}

func NewUserApplicationService(userFactory UserFactorier, userRepository UserRepositorier, userService UserService) (*UserApplicationService, error) {
	return &UserApplicationService{userFactory: userFactory, userRepository: userRepository, userService: userService}, nil
}

func (uas *UserApplicationService) Register(name string) (err error) {
	defer func() {
		if err != nil {
			err = &RegisterError{Name: name, Message: fmt.Sprintf("userapplicationservice.Register err: %s", err), Err: err}
		}
	}()
	userName, err := NewUserName(name)
	if err != nil {
		return err
	}

	// 1. エンティティUserを生成
	user, err := uas.userFactory.Create(*userName)
	if err != nil {
		return err
	}

	isUserExists, err := uas.userService.Exists(user)
	if err != nil {
		return err
	}
	if isUserExists {
		return fmt.Errorf("user name of %s is already exists.", name)
	}

	// 2. エンティティUserを保存
	if err := uas.userRepository.Save(user); err != nil {
		return err
	}

	log.Printf("user name of %s is successfully saved", name)
	return nil
}

type RegisterError struct {
	Name    string
	Message string
	Err     error
}

func (err *RegisterError) Error() string {
	return err.Message
}

package main

import (
	"database/sql"
	"fmt"
	"log"
	"os"

	"github.com/msksgm/go-itddd-09-factory/domain/model/user"
)

func main() {
	uri := fmt.Sprintf("postgres://%s/%s?sslmode=disable&user=%s&password=%s&port=%s&timezone=Asia/Tokyo",
		os.Getenv("DB_HOST"), os.Getenv("DB_NAME"), os.Getenv("DB_USER"), os.Getenv("DB_PASSWORD"), os.Getenv("DB_PORT"))
	db, err := sql.Open("postgres", uri)
	if err != nil {
		panic(err)
	}
	if err := db.Ping(); err != nil {
		panic(err)
	}
	log.Println("successfully connected to database")

	userFactory, err := user.NewUserFactory()
	if err != nil {
		panic(err)
	}
	userRepository, err := user.NewUserRepository(db)
	if err != nil {
		panic(err)
	}
	userService, err := user.NewUserService(userRepository)
	if err != nil {
		panic(err)
	}

	userApplicationService, err := user.NewUserApplicationService(userFactory, userRepository, *userService)
	if err != nil {
		panic(err)
	}

	if err := userApplicationService.Register("test-user"); err != nil {
		log.Fatal(err)
	}
}

> make up
docker compose up -d
# 完了までまつ

> make run-migration
docker compose exec app bash db-migration.sh
1/u user (13.817ms)

> make run
docker compose exec app go run main.go
2022/04/14 21:36:19 successfully connected to database
2022/04/14 21:36:19 user name of test-user is successfully saved

> make run
docker compose exec app go run main.go
2022/04/14 21:36:30 successfully connected to database
2022/04/14 21:36:30 userapplicationservice.Register err: user name of test-user is already exists.
exit status 1
make: *** [run] Error 1