发现一个高逼格的golang“构造函数”写法

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)
}

如上，最近看grpc的源码，发现了里面一种高逼格的构造函数的写法，表示震惊，学到了新姿势。

package main

import (
    "fmt"
)

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

func (o *options) writeA(a int64) *options {
    o.a = a
    return o
}
func (o *options) writeB(b string) *options {
    o.b = b
    return o
}

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

func main() {
    op := new(options)
    op.writeA(int64(1)).writeB("test").writeC(make(map[int]string, 0))

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