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

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: float64value: 3.4type: float64kind: float64value: 3.43.4value is 3.40e+003.4

反射获取结构体

package mainimport (    "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.gomain.Student{stu01 18 92}struct{stu01 18 92}{stu01 18 92} main.StudentPS 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.goget value  interface{} 100string val:100100PS E:\golang\go_pro\src\safly>

反射调用结构体方法

package mainimport (    "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<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.Value    val.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} structstruct has 3 field0 string1 int2 float32struct 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  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;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.Value    val.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} ptrstruct has 3 field0 string1 int2 float32struct 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   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.goTag:stu_namePS E:\golang\go_pro\src\safly>

练习例子

package mainimport (    "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.go0: A int = 231: B string = skidoot is now {77 Sunset Strip}PS E:\golang\go_pro\src\safly>