constructor-hell-solution.go

// https://github.com/zekroTJA/shinpuru/blob/b0900fdb90d4b69a7d8e77ac73c12da25e552a0d/internal/core/webserver/v1/controllers/guilds.go#L32-L36

func (c *GuildsController) Setup(container di.Container, router fiber.Router) {
	c.session = container.Get(static.DiDiscordSession).(*discordgo.Session)
	c.cfg = container.Get(static.DiConfig).(*config.Config)
	c.db = container.Get(static.DiDatabase).(database.Database)
	c.pmw = container.Get(static.DiPermissionMiddleware).(*middleware.PermissionsMiddleware)
// ...

constructor-hell.go

// https://github.com/zekroTJA/shinpuru/blob/d52c1c18f8a994a6a70c9a991617ab3dd4456010/internal/core/webserver/webserver.go#L70-L75

// New creates a new instance of WebServer consuming the passed
// database provider, storage provider, discordgo session, command
// handler, life cycle timer and configuration.
func New(db database.Database, st storage.Storage, s *discordgo.Session,
	cmd shireikan.Handler, lct *lctimer.LifeCycleTimer, config *config.Config,
	pmw *middleware.PermissionsMiddleware, ota *onetimeauth.OneTimeAuth) (ws *WebServer, err error) {
// ...

di-constructor-decoupled.go

package main

import "fmt"

type DBService interface {
	GetUser(email string) string
}

type EMailService interface {
	SendMail(address, content string)
}

type MyDBService struct{}

func (db *MyDBService) GetUser(email string) string {
	return "john.doe"
}

type MyEMailService struct{}

func (e *MyEMailService) SendMail(address, content string) {
	fmt.Printf("Send mail to '%s' with content '%s'\n", address, content)
}

type MyAPIService struct {
	db   DBService
	mail EMailService
}

func NewMyAPIService(db DBService, mail EMailService) *MyAPIService {
	return &MyAPIService{db, mail}
}

func (api *MyAPIService) ResetPassword(address string) {
	username := api.db.GetUser(address)
	if username != "" {
		api.mail.SendMail(address,
			fmt.Sprintf("Password reset for user '%s': ...", username))
	}
}

func main() {
	db := new(MyDBService)
	mail := new(MyEMailService)
	api := NewMyAPIService(db, mail)

	api.ResetPassword("jhon.doe@example.com")
}

di-constructor-direct.go

package main

import "fmt"

type MyDBService struct{}

func (db *MyDBService) GetUser(email string) string {
	return "john.doe"
}

type MyEMailService struct{}

func (e *MyEMailService) SendMail(address, content string) {
	fmt.Printf("Send mail to '%s' with content '%s'\n", address, content)
}

type MyAPIService struct {
	db   *MyDBService
	mail *MyEMailService
}

func NewMyAPIService(db *MyDBService, mail *MyEMailService) *MyAPIService {
	return &MyAPIService{db, mail}
}

func (api *MyAPIService) ResetPassword(address string) {
	username := api.db.GetUser(address)
	if username != "" {
		api.mail.SendMail(address,
			fmt.Sprintf("Password reset for user '%s': ...", username))
	}
}

func main() {
	db := new(MyDBService)
	mail := new(MyEMailService)
	api := NewMyAPIService(db, mail)

	api.ResetPassword("jhon.doe@example.com")
}

di-main.go

// https://github.com/zekroTJA/shinpuru/blob/b0900fdb90d4b69a7d8e77ac73c12da25e552a0d/cmd/shinpuru/main.go

func main() {
	// Parse command line flags
	flag.Parse()

	// Initialize dependency injection builder
	diBuilder, _ := di.NewBuilder()

    // ...

	// Initialize config
	diBuilder.Add(di.Def{
		Name: static.DiConfig,
		Build: func(ctn di.Container) (interface{}, error) {
			return inits.InitConfig(*flagConfigLocation, ctn), nil
		},
	})

	// Initialize database middleware and shutdown routine
	diBuilder.Add(di.Def{
		Name: static.DiDatabase,
		Build: func(ctn di.Container) (interface{}, error) {
			return inits.InitDatabase(ctn), nil
		},
		Close: func(obj interface{}) error {
			database := obj.(database.Database)
			util.Log.Info("Shutting down database connection...")
			database.Close()
			return nil
		},
	})

	// ...

	// Initialize permissions command handler middleware
	diBuilder.Add(di.Def{
		Name: static.DiPermissionMiddleware,
		Build: func(ctn di.Container) (interface{}, error) {
			return inits.InitPermissionMiddleware(ctn), nil
		},
	})

	// ...

	// Initialize discord bot session and shutdown routine
	diBuilder.Add(di.Def{
		Name: static.DiDiscordSession,
		Build: func(ctn di.Container) (interface{}, error) {
			return inits.InitDiscordBotSession(ctn), nil
		},
		Close: func(obj interface{}) error {
			session := obj.(*discordgo.Session)
			util.Log.Info("Shutting down bot session...")
			session.Close()
			return nil
		},
	})

	// ...

	// Build dependency injection container
	ctn := diBuilder.Build()
	
	// ...