《The Go Programming Language》笔记

Golang的反射由reflect包提供支持，有两个重要类型：一个Type表示一个Go类型，它是一个接口。一个Value可以持有任意类型的值。

import (
    "fmt"
    "reflect"
    "strconv"
)

func Display(name string,x interface{}) {
    fmt.Printf("Display %s (%T):\n",name,x)
    display(name,reflect.ValueOf(x))
}

func formatAtom(v reflect.Value) string {
    switch v.Kind() {
    case reflect.Invalid:
        return "invalid"
    case reflect.Int,reflect.Int8,reflect.Int16,reflect.Int32,reflect.Int64:
        return strconv.FormatInt(v.Int(),10)
    case reflect.Uint,reflect.Uint8,reflect.Uint16,reflect.Uint32,reflect.Uint64:
        return strconv.FormatUint(v.Uint(),10)
    case reflect.Bool:
        return strconv.FormatBool(v.Bool())
    case reflect.String:
        return strconv.Quote(v.String())
    case reflect.Chan,reflect.Func,reflect.Ptr,reflect.Slice,reflect.Map:
        return v.Type().String() + "0x" + strconv.FormatUint(uint64(v.Pointer()),16)
    default:
        return v.Type().String() + "value"
    }
}

func display(path string,v reflect.Value) {
    switch v.Kind() {
    case reflect.Invalid:
        fmt.Printf("%s = invalid\n",path)
    case reflect.Slice,reflect.Array:
        for i := 0; i < v.Len(); i++ {
            display(fmt.Sprintf("%s[%d]",path,i),v.Index(i))
        }
    case reflect.Struct:
        for i := 0; i < v.NumField(); i++ {
            fieldPath := fmt.Sprintf("%s.%s",v.Type().Field(i).Name)
            display(fieldPath,v.Field(i))
        }
    case reflect.Map:
        for _,key := range v.MapKeys(){
            display(fmt.Sprintf("%s[%s]",formatAtom(key)),v.MapIndex(key))
        }
    case reflect.Ptr:
        if v.IsNil() {
            fmt.Printf("%s = nil\n",path)
        } else {
            display(fmt.Sprintf("*%s",path),v.Elem())
        }
    case reflect.Interface:
        if v.IsNil() {
            fmt.Printf("%s = nil\n",path)
        } else {
            fmt.Printf("%s.type = %s\n",v.Elem().Type())
            display(path+".value",v.Elem())
        }
    default:
        fmt.Printf("%s = %s\n",formatAtom(v))

    }
}

import "testing"

type Movie struct {
    Title,Subtitle string
    Year            int
    Color           bool
    Actor           map[string]string
    Oscars          []string
    Sequel          *string
}

var strangelove = Movie{
    Title:    "Dr. Strangelove",Subtitle: "How I Learned to Stop Worrying and Love the Bomb",Year:     1964,Color:    false,Actor: map[string]string{
        "Dr. Strangelove":           "Peter Sellers","Grp. Cat. Lionel Mandrake": "Peter Sellers","Gen. Buck Turgidson":       "George Hayden",},Oscars: []string{
        "Best Actor (Nomin.)","Best Adapted Screeenplay (Nomin.)",}

func TestDisplay(t *testing.T) {
    Display("strangelove",strangelove)
}

Display strangelove (main.Movie): strangelove.Title = “Dr. Strangelove” strangelove.Subtitle = “How I Learned to Stop Worrying and Love the Bomb” strangelove.Year = 1964 strangelove.Color = false strangelove.Actor[“Dr. Strangelove”] = “Peter Sellers” strangelove.Actor[“Grp. Cat. Lionel Mandrake”] = “Peter Sellers” strangelove.Actor[“Gen. Buck Turgidson”] = “George Hayden” strangelove.Oscars[0] = “Best Actor (Nomin.)” strangelove.Oscars[1] = “Best Adapted Screeenplay (Nomin.)” strangelove.Sequel = nil