golang之reflect

￡神魔★判官ぃ 2022-01-05 10:51 279阅读 0赞

reflect，反射。

利用reflect，可以得到一个struct的相关信息。

package main
    
    import (
    	"fmt"
    	"reflect"
    )
    
    type User struct {
    	Id int
    	Name string
    	Age int
    }
    
    func (u User) Hello(name string) {
    	fmt.Printf("hello %s, my name is %s\n", name, u.Name)
    }
    
    type Manager struct {
    	User
    	title string
    }
    
    func main() {
    	// modify variable through reflect
    	//x := 123
    	//v := reflect.ValueOf(&x)
    	//v.Elem().SetInt(234)
    	//fmt.Println(x)
    
    	u := User{1, "xiaoming", 12}
    	u.Hello("atom")
    
    	// call method through reflect
    	v := reflect.ValueOf(u)
    	mv := v.MethodByName("Hello")
    	args := []reflect.Value{reflect.ValueOf("jack")}
    	mv.Call(args)
    
    	Info(u)
    	Set(&u)
    	Info(u)
    
    	m := Manager{User{1, "xiaoming", 12}, "rd"}
    	// get nested struct field
    	t := reflect.TypeOf(m)
    	fmt.Printf("%#v\n", t.Field(0))
    	fmt.Printf("%#v\n", t.FieldByIndex([]int{0,0}))
    }
    
    func Info(i interface{}) {
    	t := reflect.TypeOf(i)
    
    	if t.Kind() != reflect.Struct {
    		fmt.Println("Type Error")
    		return
    	}
    	fmt.Println("Type:", t.Name())
    
    	v := reflect.ValueOf(i)
    
    	// get fields
    	fmt.Println("Fields:")
    	for i := 0; i < t.NumField(); i++ {
    		f := t.Field(i)
    		val := v.Field(i).Interface()
    		fmt.Printf("%6s: %v = %v\n", f.Name, f.Type, val)
    	}
    	// get methods
    	fmt.Println("Methods:")
    	for i := 0; i < t.NumMethod(); i++ {
    		m := t.Method(i)
    		fmt.Printf("%6s: %v\n", m.Name, m.Type)
    	}
    }
    
    func Set(i interface{}) {
    	v := reflect.ValueOf(i)
    	if v.Kind() != reflect.Ptr || !v.Elem().CanSet() {
    		fmt.Println("Error")
    		return
    	} else {
    		v = v.Elem()
    	}
    
    	f := v.FieldByName("Name")
    	if !f.IsValid() {
    		fmt.Println("Bad Field")
    	}
    	if f.Kind() == reflect.String {
    		f.SetString("byebye")
    	}
    }

输出如下:

hello atom, my name is xiaoming  
hello jack, my name is xiaoming

Type: User  
Fields:  
Id: int = 1  
Name: string = xiaoming  
Age: int = 12  
Methods:  
Hello: func(main.User, string)

Type: User  
Fields:  
Id: int = 1  
Name: string = byebye  
Age: int = 12  
Methods:  
Hello: func(main.User, string)

reflect.StructField\{Name:"User", PkgPath:"", Type:(\*reflect.rtype)(0x10d9e00), Tag:"", Offset:0x0, Index:\[\]int\{0\}, Anonymous:true\}  
reflect.StructField\{Name:"Id", PkgPath:"", Type:(\*reflect.rtype)(0x10c4e60), Tag:"", Offset:0x0, Index:\[\]int\{0\}, Anonymous:false\}

需要注意的一个地方是:

结构体的field首字母需要大写，否则会报错"panic: reflect.Value.Interface: cannot return value obtained from unexported field or method"

参考资料

[Go编程基础][Go]

转载于:https://www.cnblogs.com/gattaca/p/8569596.html

[Go]: http://study.163.com/course/courseMain.htm?courseId=306002