golang构造函数

构造函数

type Person {
    name string,
    age    int64,
    country string,
    ...
}

func NewPerson(name string,age int64,country sting)*Person{
      return &Person{ name: name,
}

package main

import (
    "fmt"
)

type options struct {
    a int64
    b string
    c map[int]string
}

func NewOption(opt ...ServerOption) *options {
    r := new(options)
    for _, o := range opt {
        o(r)
    }
    return r
}

type ServerOption func(*options)

func WriteA(s int64) ServerOption {
    return func(o *options) {
        o.a = s
    }
}

func WriteB(s string) ServerOption {
    return func(o *options) {
        o.b = s
    }
}

func WriteC(s map[int]string) ServerOption {
    return func(o *options) {
        o.c = s
    }
}

func main() {
    opt1 := WriteA(int64(1))
    opt2 := WriteB("test")
    opt3 := WriteC(make(map[int]string,0))

    op := NewOption(opt1, opt2, opt3)

    fmt.Println(op.a, op.b, op.c)
}

func NewServer(addr string, options ...func(*Server)) (*Server, error) {
    srv := &Server{
    Addr: addr,
 }
 
   for _, option := range options {
       option(srv)
    }
 
   return srv
}
 
func timeout(d time.Duration) func(*Server) {
    return func(srv *Server) {
        srv.timeout = d
    }
}
 
func tls(c *config) func(*Server) {
    return func(srv *Server) {
        Tls := loadConfig(c)
        srv.tls = Tls
    }
}
 
//使用
src, err = NewServer("localhost:8080", timeout(1), tls(path/to/cert))

类工厂模式

// 存放 <cond, handler> 对应关系
var mux map[string]func(option *Option) error
 
// 注册handler
func register(key string, f func(option *Option) error) {
    if mux == nil {
        mux = make(map[string]func(option *Option) error)
    }
    if _, exist := mux[key]; exist {
        return errors.New("handler exist")
    }
    mux[key] = f
}
 
// factory
func factory(option *Option) error {
    return mux[option.Key](option)
}