如何在Go中创建变量类型的切片

Question

我有一个函数

func doSome(v interface{}) {
}  

如果通过指针将struct的切片传递给函数，则函数必须填充该切片。

type Color struct {
}
type Brush struct {
}
var c []Color
doSome(&c) // after с is array contains 3 elements type Color
var b []Brush
doSome(&b) // after b is array contains 3 elements type Brush

也许我需要使用反射，但是如何使用呢?

Answer 1

func doSome(v interface{}) {
    s := reflect.TypeOf(v).Elem()
    slice := reflect.MakeSlice(s, 3, 3)
    reflect.ValueOf(v).Elem().Set(slice)
}  

Answer 2

package main
import "fmt"
func doSome(v interface{}) {
  switch v := v.(type) {
  case *[]Color:
    *v = []Color{Color{0}, Color{128}, Color{255}}
  case *[]Brush:
    *v = []Brush{Brush{true}, Brush{true}, Brush{false}}
  default:
    panic("unsupported doSome input")
  }
}  
type Color struct {
    r uint8
}
type Brush struct {
    round bool
}
func main(){
    var c []Color
    doSome(&c) // after с is array contains 3 elements type Color
    var b []Brush
    doSome(&b) // after b is array contains 3 elements type Brush
    fmt.Println(b)
    fmt.Println(c)
}

Answer 3

Go没有泛型。你的可能性是:

界面调度

type CanTraverse interface {
    Get(int) interface{}
    Len() int
}
type Colours []Colour
func (c Colours) Get(i int) interface{} {
    return c[i]
}
func (c Colours) Len() int {
    return len(c)
}
func doSome(v CanTraverse) {
    for i := 0; i < v.Len; i++ {
        fmt.Println(v.Get(i))
    }
}

按@Plato建议的类型切换

func doSome(v interface{}) {
  switch v := v.(type) {
  case *[]Colour:
    //Do something with colours
  case *[]Brush:
    //Do something with brushes
  default:
    panic("unsupported doSome input")
  }
}

反射，如fmt.Println()。反射功能非常强大，但是非常昂贵，代码可能很慢。最小的示例

func doSome(v interface{}) {
    value := reflect.ValueOf(v)
    if value.Kind() == reflect.Slice {
        for i := 0; i < value.Len(); i++ {
            element := value.Slice(i, i+1)
            fmt.Println(element)
        }
    } else {
        fmt.Println("It's not a slice")
    }
}