gopt

README

gopt

Generic Functional Options for Go.

Installation

$ go get -u github.com/RussellLuo/gopt

Quick Start

package main

import (
	"fmt"

	"github.com/RussellLuo/gopt"
)

type Server struct {
	host string
	port int
}

func New(options ...gopt.Option[*Server]) *Server {
	return gopt.Apply(new(Server), options...)
}

// ServerOption holds all option factories for Server.
type ServerOption struct{}

func (ServerOption) Host(host string) gopt.Option[*Server] {
	return func(s *Server) { s.host = host }
}

func (ServerOption) Port(port int) gopt.Option[*Server] {
	return func(s *Server) { s.port = port }
}

func main() {
	server := New(
		ServerOption{}.Host("localhost"),
		ServerOption{}.Port(8080),
	)
	fmt.Printf("server: %+v\n", server)

	// Output:
	// server: &{host:localhost port:8080}
}

FAQ

1. Why might I want to use this tiny library?

   Traditional Functional Options will define many exported functions, which is likely to cause naming conflicts.

   Reference articles:

   • Golang Functional Options Pattern
   • Go Patterns' Functional Options

   Reference projects:

   • gRPC-Go's DialOption
   • Go kit's ServerOption

2. Why is ServerOption{} used in the example?

   ServerOption is a named alias of the empty struct, whose instances are fungible and consume no space.

Unsafe gopt

Unsafe gopt is an early implementation, which is deprecated and for reference only.

License

MIT

Documentation

Overview

Example

package main

import (
	"fmt"

	"github.com/RussellLuo/gopt"
)

type Server struct {
	host string
	port int
}

func New(options ...gopt.Option[*Server]) *Server {
	return gopt.Apply(new(Server), options...)
}

// ServerOption holds all option factories for Server.
type ServerOption struct{}

func (ServerOption) Host(host string) gopt.Option[*Server] {
	return func(s *Server) { s.host = host }
}

func (ServerOption) Port(port int) gopt.Option[*Server] {
	return func(s *Server) { s.port = port }
}

func main() {
	server := New(
		ServerOption{}.Host("localhost"),
		ServerOption{}.Port(8080),
	)
	fmt.Printf("server: %+v\n", server)

}

Output:
server: &{host:localhost port:8080}

Index

• func Apply[T any](x T, options ...Option[T]) T
• type Option

Examples

• Package

Functions

func Apply

func Apply[T any](x T, options ...Option[T]) T

Apply applies all options to x.

Types

type Option

type Option[T any] func(x T)

Option sets an optional parameter for x.