golang基础

2023-08-31 20:36| 来源: 网络整理| 查看: 265

反射获取基本类型反射获取结构体Elem反射操作基本类型反射调用结构体方法Elem反射操作结构体Elem反射获取tag练习例子

反射获取基本类型

反射：可以在运行时动态获取变量的相关信息 Import (“reflect”)

a. reflect.TypeOf，获取变量的类型，返回reflect.Type类型 b. reflect.ValueOf，获取变量的值，返回reflect.Value类型 c. reflect.Value.Kind，获取变量的类别，返回一个常量 d. reflect.Value.Interface()，转换成interface{}类型

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)

输出如下：

type: float64 value: 3.4 type: float64 kind: float64 value: 3.4 3.4 value is 3.40e+00 3.4 反射获取结构体 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) fmt.Println(v) k := v.Kind() fmt.Println(k) iv := v.Interface() fmt.Println(iv) stu, ok := iv.(Student) if ok { fmt.Printf("%v %T\n", stu, stu) } } func main() { var a Student = Student{ Name: "stu01", Age: 18, Score: 92, } test(a) }

输出如下：

PS E:\golang\go_pro\src\safly> go run demo.go main.Student {stu01 18 92} struct {stu01 18 92} {stu01 18 92} main.Student PS E:\golang\go_pro\src\safly> Elem反射操作基本类型

用来获取指针指向的变量，相当于： var a *int;

func main() { var b int = 1 b = 200 testInt(&b) fmt.Println(b) } //fv.Elem()用来获取指针指向的变量 func testInt(b interface{}) { val := reflect.ValueOf(b) val.Elem().SetInt(100) c := val.Elem().Int() fmt.Printf("get value interface{} %d\n", c) fmt.Printf("string val:%d\n", val.Elem().Int()) }

输出如下：

PS E:\golang\go_pro\src\safly> go run demo.go get value interface{} 100 string val:100 100 PS E:\golang\go_pro\src\safly> 反射调用结构体方法 package main import ( "fmt" "reflect" ) type Student struct { Name string Age int Score float32 } func (s Student) Print(){ fmt.Println(s) } func (s Student) Set(name string,age int,score float32){ s.Age = age s.Name = name s.Score = score } func TestStruct(a interface{}) { val := reflect.ValueOf(a) kd := val.Kind() fmt.Println(val,kd) if kd != reflect.Struct { fmt.Println("expect struct") return } //获取字段数量 fields:= val.NumField() fmt.Printf("struct has %d field\n",fields) //获取字段的类型 for i:=0;i go run demo.go {stu01 18 92.8} struct struct has 3 field 0 string 1 int 2 float32 struct has 2 methods {stu01 18 92.8} PS E:\golang\go_pro\src\safly> Elem反射操作结构体 package main import ( "fmt" "reflect" ) type Student struct { Name string Age int Score float32 } func (s Student) Print(){ fmt.Println(s) } func (s Student) Set(name string,age int,score float32){ s.Age = age s.Name = name s.Score = score } func TestStruct(a interface{}) { val := reflect.ValueOf(a) kd := val.Kind() fmt.Println(val,kd) if kd!= reflect.Ptr && val.Elem().Kind() == reflect.Struct { fmt.Println("expect struct") return } //获取字段数量 fields:= val.Elem().NumField() fmt.Printf("struct has %d field\n",fields) //获取字段的类型 for i:=0;istu01 18 92.8} ptr struct has 3 field 0 string 1 int 2 float32 struct has 2 methods {stu01 18 92.8} PS E:\golang\go_pro\src\safly> Elem反射获取tag package main import ( "fmt" "reflect" ) type Student struct { Name string `json:"stu_name"` Age int Score float32 } func (s Student) Print(){ fmt.Println(s) } func (s Student) Set(name string,age int,score float32){ s.Age = age s.Name = name s.Score = score } func TestStruct(a interface{}) { typ := reflect.TypeOf(a) tag := typ.Elem().Field(0).Tag.Get("json") fmt.Printf("Tag:%s\n",tag) } func main() { var a Student = Student{ Name: "stu01", Age: 18, Score: 92.8, } TestStruct(&a) }

输出如下：

PS E:\golang\go_pro\src\safly> go run demo.go Tag:stu_name PS E:\golang\go_pro\src\safly> 练习例子 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) }

输出如下：

PS E:\golang\go_pro\src\safly> go run demo.go 0: A int = 23 1: B string = skidoo t is now {77 Sunset Strip} PS E:\golang\go_pro\src\safly>

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