golang基础-反射获取（基础数据、结构体）、操作（基本类型、结构体、指针）、反射获取Tag

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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 = 3.4fmt.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 mainimport ("fmt""reflect"
)type Student struct {Name  stringAge   intScore 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 = 1b = 200testInt(&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 mainimport ("fmt""reflect"
)type Student struct {Name  stringAge   intScore float32}func (s Student) Print(){fmt.Println(s)
}func (s Student) Set(name string,age int,score float32){s.Age = ages.Name = names.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<fields;i++{fmt.Printf("%d %v\n",i,val.Field(i).Kind())}//获取方法数量methods:=val.NumMethod()fmt.Printf("struct has %d methods\n",methods)//反射调用的Print方法var params []reflect.Valueval.Method(0).Call(params)}func main() {var a Student = Student{Name:  "stu01",Age:   18,Score: 92.8,}TestStruct(a)// fmt.Println(a)
}

输出如下：

PS E:\golang\go_pro\src\safly> 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 mainimport ("fmt""reflect"
)type Student struct {Name  stringAge   intScore float32}func (s Student) Print(){fmt.Println(s)
}func (s Student) Set(name string,age int,score float32){s.Age = ages.Name = names.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;i<fields;i++{fmt.Printf("%d %v\n",i,val.Elem().Field(i).Kind())}//获取方法数量methods:=val.NumMethod()fmt.Printf("struct has %d methods\n",methods)//反射调用的Print方法var params []reflect.Valueval.Elem().Method(0).Call(params)
}func main() {var a Student = Student{Name:  "stu01",Age:   18,Score: 92.8,}TestStruct(&a)// fmt.Println(a)
}

输出如下：

PS E:\golang\go_pro\src\safly> go run demo.go
&{stu01 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 mainimport ("fmt""reflect"
)type Student struct {Name  string `json:"stu_name"`Age   intScore float32}func (s Student) Print(){fmt.Println(s)
}func (s Student) Set(name string,age int,score float32){s.Age = ages.Name = names.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 mainimport ("fmt""reflect"
)type T struct {A intB 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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