Golang Reflex Reflection

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Reflective Reflection

• Reflection can greatly increase the flexibility of the program, so that interface{} has a greater scope of play
• Reflection uses the TypeOf and valueof functions to get target object information from the interface
• Reflection will use anonymous fields as separate fields (anonymous field nature)
• You want to use reflection to modify the state of an object, if Interface.data is settable, which is pointer-interface
• The method can be called "dynamic" by reflection

Basic operation of reflection on a struct

package mainimport (    "fmt"    "reflect")type User struct {    Id   int    Name string    Age  int}func (u User) Hello() {    fmt.Println("Hello world!")}func Info(o interface{}) {    t := reflect.TypeOf(o)         //反射使用 TypeOf 和 ValueOf 函数从接口中获取目标对象信息    fmt.Println("Type:", t.Name()) //调用t.Name方法来获取这个类型的名称    v := reflect.ValueOf(o) //打印出所包含的字段    fmt.Println("Fields:")    for i := 0; i < t.NumField(); i++ { //通过索引来取得它的所有字段，这里通过t.NumField来获取它多拥有的字段数量，同时来决定循环的次数        f := t.Field(i)               //通过这个i作为它的索引，从0开始来取得它的字段        val := v.Field(i).Interface() //通过interface方法来取出这个字段所对应的值        fmt.Printf("%6s:%v =%v\n", f.Name, f.Type, val)    }    for i := 0; i < t.NumMethod(); i++ { //这里同样通过t.NumMethod来获取它拥有的方法的数量，来决定循环的次数        m := t.Method(i)        fmt.Printf("%6s:%v\n", m.Name, m.Type)    }}func main() {    u := User{1, "Jack", 23}    Info(u)}

Determine if the incoming type is the type we want

Package Mainimport ("FMT" "reflect") type User struct {Id int Name string Age int}func (U User) Hello () {FMT. Println ("Hello world!")} Func Info (o interface{}) {t: = reflect. TypeOf (o)//reflection uses the TypeOf and VALUEOF functions to obtain the target object information from the interface FMT. Println ("Type:", T.name ())//Call T. The name method is used to get the names of this type if k: = T.kind (); K! = reflect. Struct {//The kind method is used to determine if the incoming type is the type FMT we need to reflect. Println ("XX") return} V: = reflect. ValueOf (o)//print out the included fields in FMT. Println ("Fields:") for I: = 0; I < T.numfield (); i++ {//through the index to get all of its fields, here through T. Numfield to get the number of fields it has, and also to determine how many cycles f: = T.field (i)//through this I as its index, starting from 0 to get its field val: = V.field (i). Interface ()//Use the Interface method to remove the value of this field for FMT. Printf ("%6s:%v =%v\n", F.name, F.type, Val)} for I: = 0; I < T.nummethod (); i++ {//here also through T. Nummethod to get the number of methods it has to determine the number of cycles m: = T.method (i) fmt.   Printf ("%6s:%v\n", M.name, M.type)}}func main () {u: = user{1, "Jack", 23} Info (U)} 

Reflect anonymous or embedded fields

package mainimport (    "fmt"    "reflect")type User struct {    Id   int    Name string    Age  int}type Manager struct {    User  //反射会将匿名字段作为一个独立字段来处理    Title string}func main() {    m := Manager{User: User{1, "Jack", 12}, Title: "123"}    t := reflect.TypeOf(m)    fmt.Printf("%#v\n", t.Field(0))                   //#号会将reflect的struct的详情页打印出来，可以看出来这是一个匿名字段    fmt.Printf("%#v \n", t.FieldByIndex([]int{0, 0})) //此时 我们就可以将User当中的ID取出来,这里面需要传进方法中的是一个int类型的slice，User相对于manager索引是0，id相对于User索引也是0    fmt.Printf("%v \n", t.FieldByIndex([]int{0, 1}))    v := reflect.ValueOf(m)    fmt.Printf("%#v\n", v.Field(0))}

Modify the contents of a struct by reflection

package mainimport (    "fmt"    "reflect")func main() {    x := 123    v := reflect.ValueOf(&x)       //传递指针才能修改    v.Elem().SetInt(999)    fmt.Println(x)}PS G:\mygo\src\mytest> go run .\temp10.go999

package mainimport (    "fmt"    "reflect")type User struct {    Id   int    Name string    Age  int}func main() {    u := User{1, "Tom", 12}    Set(&u)    fmt.Println(u)}func Set(o interface{}) {    v := reflect.ValueOf(o)    if v.Kind() == reflect.Ptr && !v.Elem().CanSet() {        fmt.Println("xxx")        return    } else {        v = v.Elem()    }    f := v.FieldByName("Name")    if !f.IsValid() {        fmt.Println("xiugaishibai")    }    if f.Kind() == reflect.String {        f.SetString("jACK")    }}

Invoking methods dynamically by means of the firing method

  Package Mainimport ("FMT" "reflect") type User struct {Id int. Name string Age int}func (U Us ER) Hello (name string) {FMT. Println ("Hello", Name, "My name is", U.name)}func main () {u: = user{1, "OK", "k} V: = reflect. ValueOf (u) MV: = V.methodbyname ("Hello") args: = []reflect. Value{reflect. ValueOf ("JOE")} mv. Call (args)}