golang实现参数可变的技巧

Go 使用默认参数的技巧

Functional Options Pattern in Go

golang中没有函数默认参数的设计，所以须要些特别的技巧来实现。
假如咱们须要订购一批电脑，其中电脑配置cpu，gpu，内存支持自定义。

type Computer interface {
  PowerOn() error
  PowerOff() error
}

type computer struct {
  name string
  cpu string
  gpu string
  memorySize int
}

定义自定义参数配置，建立一个默认的电脑配置

type pcConfigure struct {
  cpu string
  gpu string
  memorySize int
}

var DefaultPConfigure = pcConfigure {
  "i3 2120",
  "GTX 660",
  12}

建立一个闭包函数，接受自定义的配置参数，返回一个自定义的参数配置

type newPcConfigure func(*pcConfigure)

func newCpuConfigure(cpu string) newPcConfigure {
  return func(o *pcConfigure) {
    o.cpu = cpu
  }
}

func newGpuConfigure(gpu string) newPcConfigure {
  return func(o *pcConfigure) {
    o.gpu = gpu
  }
}

func newMemorySizeConfigure(memorySize int) newPcConfigure {
  return func(o *pcConfigure) {
    o.memorySize = memorySize
  }
}

最后一步，定义一个构造coputer的函数，接受上面的闭包函数为参数

func newComputer(name string, opts ...newPcConfigure) *computer {
  pcConfigure := DefaultPConfigure
  for _, o := range opts {
    o(&pcConfigure)
  }
  return &computer {
    name: name,
    cpu: pcConfigure.cpu,
    gpu: pcConfigure.gpu,
    memorySize: pcConfigure.memorySize}
}

完整代码

package main
 
import (
  "fmt"
)
 
type pcConfigure struct {
  cpu string
  gpu string
  memorySize int
}

var DefaultPConfigure = pcConfigure {
  "i3 2120",
  "GTX 660",
  12}

type newPcConfigure func(*pcConfigure)

func newCpuConfigure(cpu string) newPcConfigure {
  return func(o *pcConfigure) {
    o.cpu = cpu
  }
}

func newGpuConfigure(gpu string) newPcConfigure {
  return func(o *pcConfigure) {
    o.gpu = gpu
  }
}

func newMemorySizeConfigure(memorySize int) newPcConfigure {
  return func(o *pcConfigure) {
    o.memorySize = memorySize
  }
}

type Computer interface {
  PowerOn() error
  PowerOff() error
}

type computer struct {
  name string
  cpu string
  gpu string
  memorySize int
}

func newComputer(name string, opts ...newPcConfigure) *computer {
  pcConfigure := DefaultPConfigure
  for _, o := range opts {
    o(&pcConfigure)
  }
  return &computer {
    name: name,
    cpu: pcConfigure.cpu,
    gpu: pcConfigure.gpu,
    memorySize: pcConfigure.memorySize}
}


func (c *computer) PowerOn() (err error) {
  return 
}

func (c *computer) PowerOff() (err error) {
  return 
}

func main () {
  pc1 := newComputer("pc1")
  fmt.Println(pc1)
  pc2 := newComputer("pc2", newCpuConfigure("i7 8700k"), newGpuConfigure("RTX 2080ti"))
  fmt.Println(pc2)
}