1、反射：可以在运行时动态获取变量的相关信息
Import（“reflect”）
两个函数：
reflect.TypeOf()//获取变量的类型，返回reflect.Type类型
reflect.ValueOf()//获取变量的值，返回reflect.Value类型
reflect.Value.Kind()//获取变量的类别，返回一个常量
reflect.Value.Interface()//转换成interface{}类型
可逆状态
示例用法
package main import ( "fmt" "reflect" ) type Student struct { Name string Age int Score float32 } func test(b interface{}) { t := reflect.TypeOf(b) fmt.Println(t) v := reflect.ValueOf(b) k := v.Kind() fmt.Println(k) iv := v.Interface() stu, ok := iv.(Student) if ok { fmt.Printf("%v %T\n", stu, stu) } } func testInt(b interface{}) { val := reflect.ValueOf(b) c := val.Int() fmt.Printf("get value interface{} %d\n", c) } func main() { var a Student = Student{ Name: "stu01", Age: 18, Score: 92, } test(a) testInt(1234) }
package main import ( "fmt" "reflect" ) func main(){ var x float64=3.4 fmt.Println("type:",reflect.TypeOf(x)) v:=reflect.ValueOf(x) fmt.Println("value:",v) fmt.Println("type:",v.Type()) fmt.Println("kind:",v.Kind()) fmt.Println("value:",v.Float()) fmt.Println(v.Interface()) fmt.Printf("value is %5.2e\n",v.Interface()) y:=v.Interface().(float64) fmt.Println(y) }
获取变量的值
reflect.ValueOf(x).Float()
reflect.ValueOf(x).Int()
reflect.ValueOf(x).String()
reflect.ValueOf(x).Bool()
反射之elem()修改指针的方法
package main //通过反射动态修改变量的值 import ( "fmt" "reflect" ) type Student struct { Name string Age int Score float32 } func test(b interface{}) { t := reflect.TypeOf(b) fmt.Println(t) v := reflect.ValueOf(b) k := v.Kind() fmt.Println(k) iv := v.Interface() stu, ok := iv.(Student) if ok { fmt.Printf("%v %T\n", stu, stu) } } func testInt(b interface{}) { val := reflect.ValueOf(b) val.Elem().SetInt(100) //val.Elem().Setint()相当于指针操作 c := val.Elem().Int() fmt.Printf("get value interface{}%d\n", c) fmt.Printf("string val:%d\n", val.Elem().Int()) } func main() { var a Student = Student{ Name: "stu01", Age: 18, Score: 92, } test(a) var b int = 1 b = 200 testInt(&b) fmt.Println(b) }
用反射操作结构体
reflect.Value.NumField()获取结构体中字段的个数
reflect.Value.Method(n).Call来条用结构体中的方法
反射取得结构体方法个数，字段数
package main //通过反射动态修改变量的值 import ( "fmt" "reflect" ) type Student struct { Name string Age int Score float32 Sex string } func (s Student) Set(name string, age int, score float32, sex string) { s.Name = name s.Age = age s.Score = score s.Sex = sex } func TestStruct(a interface{}) { val := reflect.ValueOf(a) kd := val.Kind() if kd != reflect.Struct { fmt.Println("expect struct") return } num := val.NumField() fmt.Printf("struct has %d fields\n", num) numOfMethod := val.NumMethod() fmt.Printf("struct has %d methods\n", numOfMethod) } func main() { var a Student a = Student{ Name: "stu01", Age: 18, Score: 92.8, } TestStruct(a) fmt.Println(a) }
反射练习
package main //通过反射动态修改变量的值 import ( "fmt" "reflect" ) type NotKnownType struct { s1 string s2 string s3 string } //定义一个String方法 func (n NotKnownType) String() string { return n.s1 + "-" + n.s2 + "-" + n.s3 } var secret interface{} = NotKnownType{"Ada", "Go", "Oberon"} func main() { value := reflect.ValueOf(secret) //<main.NotKnownType Value> typ := reflect.TypeOf(secret) //main.NotKnownType fmt.Println(typ) knd := value.Kind() //struct fmt.Println(knd) for i := 0; i < value.NumField(); i++ { fmt.Printf("Field %d:%v\n", i, value.Field(i)) } results := value.Method(0).Call(nil) fmt.Println(results)//[Ada-Go-Oberon] }
通过反射修改结构体
package main import ( "fmt" "reflect" ) type T struct { A int B string } func main() { t := T{23, "skidoo"} s := reflect.ValueOf(&t).Elem() typeOfT := s.Type() for i := 0; i < s.NumField(); i++ { f := s.Field(i) fmt.Printf("%d:%s %s=%v\n", i, typeOfT.Field(i).Name, f.Type(), f.Interface()) } s.Field(0).SetInt(77) s.Field(1).SetString("Sunset Strip") fmt.Println("t is now", t) }
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