Golang Reflect Bag

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Reflect Bag

The Reflect Reflex Pack has 2 important types, which are passed Typeof() and ValueOf() returned respectively. Separately in the package of the source code package reflect type.go andvalue.go

Type

TypeOf () returns an Type interface type, in the source code

type Type interface {Align() intFieldAlign() intMethod(int) MethodMethodByName(string) (Method, bool)NumMethod() intName() stringPkgPath() stringSize() uintptrString() stringKind() KindImplements(u Type) boolConvertibleTo(u Type) boolComparable() boolBits() intChanDir() ChanDirIsVariadic() boolElem() TypeField(i int) StructFieldFieldByIndex(index []int) StructFieldFieldByName(name string) (StructField, bool)FieldByNameFunc(match func(string) bool) (StructField, bool)In(i int) TypeKey() TypeLen() intNumField() intNumIn() intNumOut() intOut(i int) Typecommon() *rtypeuncommon() *uncommonType}

There is a rtype struct that implements Type all the methods of the interface. Source:

type rtype struct {size       uintptrptrdata    uintptr  hash       uint32  tflag      tflag    align      uint8    fieldAlign uint8    kind       uint8   alg        *typeAlg gcdata     *byte    str        nameOff ptrToThis  typeOff }

TypeOf will return a rtype. Can call his method.

For example:

argTest := "test"v :=reflect.TypeOf(argTest)fmt.Println(v.Kind()) //stringargTest1 :=&testStruct{}v1 :=reflect.TypeOf(argTest1)fmt.Println(v1.Kind()) //  ptrargTest1 :=&testStruct{}v1 :=reflect.TypeOf(*argTest1)fmt.Println(v1.Kind()) //structargTest1 :=&testStruct{}v1 :=reflect.TypeOf(argTest1).Elem()fmt.Println(v1.Kind()) // struct

The method can be used Kind() to get the type of the reflected object, if the struct type is passed in an address, it gets the ptr type, it can pass in the value of the address, or Elem() the corresponding type can be obtained by using the method. The basic properties of all underlying types are available through rtype . The underlying type can view Kind the inclusions in the Type.go type.

Gets the properties of all the elements in the struct.

func getStructArgProperty(t interface{}){var v reflect.Typeif  reflect.TypeOf(t).Kind() == reflect.Ptr {if reflect.TypeOf(t).Elem().Kind() != reflect.Struct{fmt.Println("不是结构体")return}v =reflect.TypeOf(t).Elem()}else{if reflect.TypeOf(t).Kind() != reflect.Struct{fmt.Println("不是结构体")return}v=reflect.TypeOf(t)}run(v)}func run(v reflect.Type){for  i:=0;i<v.NumField();i++{argType:= v.Field(i)if argType.Type.Kind() ==reflect.Ptr {fmt.Println(argType.Name,argType.Type.Elem().Kind())}else {if argType.Type.Kind() ==reflect.Struct {fmt.Println("   =====>",argType.Name)run(argType.Type)}else {fmt.Println(argType.Name, argType.Type.Kind())}}}}

However, to fetch the value of an object, you need to use the valueof.

Value

ValueOf () returns a Value struct type, in source code

type Value struct {typ *rtypeptr unsafe.Pointerflag}

The rtype Kind() difference is that the flag is a uintptr type that implements the kind() method. New type, in the source code

const (flagKindWidth        = 5 // there are 27 kindsflagKindMask    flag = 1<<flagKindWidth - 1flagStickyRO    flag = 1 << 5flagEmbedRO     flag = 1 << 6flagIndir       flag = 1 << 7flagAddr        flag = 1 << 8flagMethod      flag = 1 << 9flagMethodShift      = 10flagRO          flag = flagStickyRO | flagEmbedRO)

Using ValueOf values to assign values

arr := [...]int{1,2,3,4}v := reflect.ValueOf(arr)fmt.Println(v)  //[1,2,3,4]v1 := reflect.ValueOf(&arr)fmt.Println(v1) //&[1,2,3,4]fmt.Println(v.Elem().CanSet())    // panicfmt.Println(v1.Elem().CanSet())   // truev1.Elem().Index(0).SetInt(10)fmt.Println(arr)  // 10,2,3,4

The

Elem () method only distinguishes between interface{} ptr , and then you need to call Elem () when handling pointer types method to get a concrete base type. You can use the Kind () method to know whether ValueOf returns a pointer or interfaec{} , and if you need to assign a value, you need to pass in a pointer to the object, which is the meaning of value passing or addressing. The value of the struct , and the assignment only calls a different method. For example:

type student struct{    numb int    name string    Age int    class *class}type class struct{    classNumber int    className string}func structValueOf(){s := student{numb:1,name:"john",Age:18,class:&class{classNumber:1}}v := reflect.ValueOf(&s)getStructArgProperty(v)}func getStructArgProperty(v reflect.Value){   for  i:=0;i<v.NumField();i++{          //NumField()会判断Kind()是否为struct 不是的话会panicargType:= v.Field(i)if argType.Kind() == reflect.Ptr{if argType.Elem().Kind() == reflect.Struct{fmt.Println("========>")getStructArgProperty(argType.Elem())}else {fmt.Println(argType.Elem().Kind(),"     : ",argType ,"   ",argType.Elem().CanSet())}}else {if argType.Kind()==reflect.Struct {getStructArgProperty(argType)}else {if argType.CanSet() == true && argType.Kind() == reflect.Int {argType.SetInt(10)}fmt.Println(argType.Kind(), "     : ", argType, "   ", argType.CanSet())}}}}

The properties of the field structure body that need to be modified should be public.

Types of methods

To get the method of a type, use TypeOf() the ValueOf() 2 type to get it.

The difference is that the TypeOf() basic properties of the return method, but not the actual call method, but by calling ValueOf Call() , and ValueOf then not returning the name of the method and other basic properties

type myType intfunc (my *myType) Hi(){fmt.Println("my value ",*my)}func (my *myType) Set(x int){*my = myType(x)}func (my myType) Get() int{fmt.Println("my value ", my)return int(my)}var s myType = 1v := reflect.ValueOf(&s)v1 := reflect.TypeOf(s)fmt.Println(" v  ",v.NumMethod())   //3fmt.Println(" v1  ",v1.NumMethod())   //1  传入的如果是值类型，则只返回值类型方法for i:=0;i<v1.NumMethod();i++{fmt.Println(v1.Method(i))   //方法名等结果，根据首字母排序}for i:=0;i<v.NumMethod();i++{fmt.Println(v.Method(i))    //reflect方法对象。}var para []reflect.Valuepara = append(para,reflect.ValueOf(11))fmt.Println(v.Method(2).Call(para))   //调用Set方法para  = append(para,reflect.ValueOf(&s))fmt.Println(v1.Method(0).Func.Call(para[1:]))  //调用Get方法