利用reflect设置struct的字段

极为重要的两篇文章

1. http://speakmy.name/2014/09/14/modifying-interfaced-go-struct/

Combining it all together, this is the final function:

func Destroy(subj interface{}) {
	stype := reflect.ValueOf(subj).Elem()
	field := stype.FieldByName("Status")
	if field.IsValid() {
		field.SetString("Destroyed")
	}
}

func TestDestroy(t *testing.T) {
	// Initialize data
	jaeger := Jaeger{Name: "Cherno Alpha", Country: "RU", Status: "Active"}
	kaiju := Kaiju{Alias: "Scissure", Origin: "Sydney", Status: "Unknown"}
	shatterdome := Shatterdome{Location: "Lima"}

	// Destroy everything
	Destroy(&jaeger)
	Destroy(&kaiju)
	Destroy(&shatterdome)

	// Check the result
	if jaeger.Status != "Destroy" {
		t.Error("jaeger was not destroyed")
	}
	if kaiju.Status != "Destroy" {
		t.Error("kaiju was not destroyed")
	}
}

2.

参考golang反射三大规则

reflect.Value区分CanSet和Can not Set的, 所以, 必须要返回成Can set的reflect.Value
如:

s := reflect.ValueOf(&t).Elem()

然后就可以happy的设值了, 可是不能随便设值的, 一个通用的方法就是使用Set(v Value)方法, 所以之前必须将值转成reflect.Value类型, 下面的这段代码就是转成Value类型

sliceValue := reflect.ValueOf([]int{1, 2, 3}) // 这里将slice转成reflect.Value类型

完整参考:

type T struct {
    Age int
    Name string
    Children []int
}
t := T{12, "someone-life", nil}
s := reflect.ValueOf(&t).Elem()

s.Field(0).SetInt(123) // 内置常用类型的设值方法
sliceValue := reflect.ValueOf([]int{1, 2, 3}) // 这里将slice转成reflect.Value类型
s.FieldByName("Children").Set(sliceValue)

###############

How to use Reflect to set a struct field

http://samwize.com/2015/03/20/how-to-use-reflect-to-set-a-struct-field/

In short, if you want to set a struct foo object when you know the field name to set, this is the code:

func setFoo ( foo * Foo , field string , value string ) {

v := reflect . ValueOf ( foo ). Elem (). FieldByName ( field )

if v . IsValid () {

v . SetString ( value )

}

}

If you want to print all the fields of foo, this is the code:

s := reflect . ValueOf ( foo ). 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 ())

}