GO機能オプションパターン

package main

import "fmt"

type Client struct {
	Id int64
	AppKey string
	AppSecret string
AppSecret string }

type Option func(*Client) // The arguments to the go function are passed as values, so if you want to modify the Client (the default value) you must pass the pointer

func WithAppKey(appKey string) Option {
	return func(client *Client) {
		client.AppKey = appKey
	AppKey = appKey }
}

func WithAppSecret(appSecret string) Option {
	return func(client *Client) {
		client.AppSecret = appSecret
	}
}

//
// NewClient
// @Description sets the parameters of a function to optional functions
// @param id Fixed parameters, or you can put all in optional opts
// @param opts
// @return Client returns *Client and Client can both be
//
func NewClient(id int64, opts . .Option) Client {
	o := Client{
		Id: id,
		AppKey: "key_123456",
		AppSecret: "secret_123456",
	}

	for _, opt := range opts {
		opt(&o) // go function arguments are value passed so to modify Client (default) you must pass the pointer
	}

	return o
}

func main() {
	// Use the default value
	fmt.Println(NewClient(1)) // {1 key_123456 secret_123456}
	// use the passed in values
	fmt.Println(NewClient(2, WithAppKey("change_key_222"))) // {2 change_key_222 secret_123456}
	// Pass in out of order
	fmt.Println(NewClient(3, WithAppSecret("change_secret_333"))) // {3 key_123456 change_secret_333}
	fmt.Println(NewClient(4, WithAppSecret("change_secret_444"), WithAppKey("change_key_444"))) // {4 change_key_444 change_secret_444}
}