函数式配置模式

functional_options_pattern_in_go

package main

import (
	"fmt"
)

var defaultStuffClient = stuffClient{
    retries: 3,
    timeout: 2,
}

type StuffClientOption func(*stuffClient)

func WithRetries(r int) StuffClientOption {
    return func(o *stuffClient) {
        o.retries = r
    }
}

func WithTimeout(t int) StuffClientOption {
    return func(o *stuffClient) {
        o.timeout = t
    }
}

type StuffClient interface {
	DoStuff() error
}
type stuffClient struct {
    conn    Connection
    timeout int
    retries int
}

type Connection struct{}

func NewStuffClient(conn Connection, opts ...StuffClientOption) StuffClient {
    client := defaultStuffClient
    for _, o := range opts {
        o(&client)
    }
	
	client.conn = conn

    return client
}

func (c stuffClient) DoStuff() error {
        return nil
}

// The Test

func main() {
	x := NewStuffClient(Connection{})
	fmt.Println(x) // prints &{{} 2 3}
	
	x = NewStuffClient(Connection{}, WithRetries(1))
        fmt.Println(x) // prints &{{} 2 1}	
}