饶全成：深度解密 Go 语言之反射（下）

package mainimport (    "reflect"    "fmt")type Child struct {    Name string    Grade int    Handsome bool}type Adult struct {    ID string `qson:"Name"`    Occupation string    Handsome bool}// 如果输⼊参数 i 是 Slice，元素是结构体，有⼀个字段名为 `Handsome`，// 并且有⼀个字段的 tag 或者字段名是 `Name` ，// 如果该 `Name` 字段的值是 `qcrao`，// 就把结构体中名为 `Handsome` 的字段值设置为 true。func handsome(i interface{}) {    // 获取 i 的反射变量 Value    v := reflect.ValueOf(i)    // 确定 v 是⼀个 Slice    if v.Kind() != reflect.Slice {        return}    // 确定 v 是的元素为结构体    if e := v.Type().Elem(); e.Kind() != reflect.Struct {        return}// 确定结构体的字段名含有 "ID" 或者 json tag 标签为 `name`// 确定结构体的字段名 "Handsome"st := v.Type().Elem()// 寻找字段名为 Name 或者 tag 的值为 Name 的字段foundName := falsefor i := 0; i < st.NumField(); i++ {    f := st.Field(i)    tag := f.Tag.Get("qson")    if (tag == "Name" || f.Name == "Name") && f.Type.Kind() == reflect.String {        foundName = true        break    }}if !foundName {    return}if niceField, foundHandsome := st.FieldByName("Handsome"); foundHandsome == false || niceField.Type.Kind() != reflect.Boo    return}// 设置名字为 "qcrao" 的对象的 "Handsome" 字段为 truefor i := 0; i < v.Len(); i++ {    e := v.Index(i)    handsome := e.FieldByName("Handsome")    // 寻找字段名为 Name 或者 tag 的值为 Name 的字段    var name reflect.Value    for j := 0; j < st.NumField(); j++ {        f := st.Field(j)        tag := f.Tag.Get("qson")        if tag == "Name" || f.Name == "Name" {            name = v.Index(i).Field(j)        }    }        if name.String() == "qcrao" {            handsome.SetBool(true)        }    }}func main() {    children := []Child{        {Name: "Ava", Grade: 3, Handsome: true},        {Name: "qcrao", Grade: 6, Handsome: false},    }    adults := []Adult{        {ID: "Steve", Occupation: "Clerk", Handsome: true},        {ID: "qcrao", Occupation: "Go Programmer", Handsome: false},    }    fmt.Printf("adults before handsome: %v\n", adults)    handsome(adults)    fmt.Printf("adults after handsome: %v\n", adults)    fmt.Println("-------------")    fmt.Printf("children before handsome: %v\n", children)    handsome(children)    fmt.Printf("children after handsome: %v\n", children)}

adults before handsome: [{Steve Clerk true} {qcrao Go Programmer false}]adults after handsome: [{Steve Clerk true} {qcrao Go Programmer true}]-------------children before handsome: [{Ava 3 true} {qcrao 6 false}]children after handsome: [{Ava 3 true} {qcrao 6 true}]

package mainimport (    "reflect"    "fmt")type Child struct {    Name string    handsome bool}func main() {    qcrao := Child{Name: "qcrao", handsome: true}    v := reflect.ValueOf(&qcrao)    f := v.Elem().FieldByName("Name")    fmt.Println(f.String())    f.SetString("stefno")    fmt.Println(f.String())    f = v.Elem().FieldByName("handsome")    // 这⼀句会导致 panic，因为 handsome 字段未导出    //f.SetBool(true)    fmt.Println(f.Bool())}

qcraostefnotrue

func Marshal(v interface{}) ([]byte, error)func Unmarshal(data []byte, v interface{}) error

func DeepEqual(x, y interface{}) bool

type MyInt inttype YourInt intfunc main() {m := MyInt(1)y := YourInt(1)fmt.Println(reflect.DeepEqual(m, y)) // false}

func DeepEqual(x, y interface{}) bool {if x == nil || y == nil {return x == y}v1 := ValueOf(x)v2 := ValueOf(y)if v1.Type() != v2.Type() {return false}return deepValueEqual(v1, v2, make(map[visit]bool), 0)}

// deepValueEqual 函数// ……case Map:if v1.IsNil() != v2.IsNil() {return false}if v1.Len() != v2.Len() {return false}if v1.Pointer() == v2.Pointer() {return true}for _, k := range v1.MapKeys() {val1 := v1.MapIndex(k)val2 := v2.MapIndex(k)if !val1.IsValid() || !val2.IsValid() || !deepValueEqual(v1.MapIndex(k), v2.MapIndex(k), visited, depth+1) {return false}}return true// ……

type visit struct {a1 unsafe.Pointera2 unsafe.Pointertyp Type}map[visit]bool

func TypeOf ( i interface{} ) Typefunc ValueOf ( i interface{} ) Value