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newc

new-* constructor generator

Doc: English | 中文


A cli tool to generate constructor code for a Golang struct.

Installation

go install github.com/Bin-Huang/newc@latest

Usage

Add a go:generate command line to the struct which you want to generate a constructor.

//go:generate newc
type UserService struct {
	baseService
	userRepository *repositories.UserRepository
	proRepository  *repositories.ProRepository
}

After executing go generate ./... the constructor code generated:

// constructor_gen.go

// NewUserService Create a new UserService
func NewUserService(baseService baseService, userRepository *repositories.UserRepository, proRepository *repositories.ProRepository) *UserService {
	return &UserService{
		baseService:    baseService,
		userRepository: userRepository,
		proRepository:  proRepository,
	}
}

See more examples here

Usage without manual installation

Recommended for team collaboration

Without manual installation, just add this comment line to the struct. Go will automatically install this tool if missing.

//go:generate go run github.com/Bin-Huang/newc@v0.8.3

For example:

//go:generate go run github.com/Bin-Huang/newc@v0.8.3
type UserService struct {
	baseService
	userRepository *repositories.UserRepository
	proRepository  *repositories.ProRepository
}

This is very useful, especially in teamwork. It can run without manual installation. It doesn't break the work of other people who don't have installed this tool in collaboration.

How to return value instead reference?

Add --value parameter

//go:generate newc --value
type Config struct {
	debug  bool
}

Generated code:

// constructor_gen.go

// NewConfig Create a new Config
func NewConfig(debug bool) Config {
	return Config{
		debug:  debug,
	}
}

How to call an initializer in constructor?

  1. Add --init parameter
  2. Write an init method for the struct
//go:generate newc --init
type Controller struct {
	logger *zap.Logger
	debug  bool
}

func (c *Controller) init() {
	c.logger = c.logger.With(zap.String("tag", "controller-debugger"))
	c.debug = true
}

Generated code:

// constructor_gen.go

// NewController Create a new Controller
func NewController(logger *zap.Logger, debug bool) *Controller {
	s := &Controller{
		logger: logger,
		debug:  debug,
	}
	s.init()
	return s
}

How to ignore some fields when generating constructor code?

Add a tag newc:"-" to fields that need to be ignored

type Forbidden struct {
	Msg    string
	Status int    `newc:"-"`
}

Generated code:

// NewForbidden Create a new Forbidden
func NewForbidden(msg string) *Forbidden {
	return &Forbidden{
		Msg: msg,
	}
}

If you think the go:generate comment is too long...

Some suggestions:

  1. Add a code snippest in your editor/IDE for the tool (suggested)
  2. ......

Features & Motivation

1. It makes your code easier to write and maintain.

Writing and updating constructor code for many structs can be laborious and error-prone, especially if you have a huge codebase. These should be handed over to automatic tools like this tool.

And it also works well with these dependency injection tools like wire. If you use wire in your project, you may need this tool very much.

2. It takes care of the generated code.

Don't worry about the imports, variable naming, and code style in the generated code.

3. It is more suitable for teamwork.

It doesn't break the work of other people who don't have installed this tool in collaboration. Go will automatically install this tool if missing.

//go:generate go run github.com/Bin-Huang/newc@v0.8.3

Sponsoring

"Buy Me A Coffee"

License

MIT

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A cli tool to generate constructor code for a Golang struct.

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