go的反射操作reflect实践

 通过反射机制，找到相应的Left或者Right广告

type SearchAdsObj struct {
	Left     PositionAdsObj `json:"left"`
	Right    PositionAdsObj `json:"right"`
}
 
func getFieldByName(obj SearchAdsObj, fieldName string) (interface{}, error) {
	fmt.Printf("getFieldByName: %s \n", fieldName)
	val := reflect.ValueOf(obj)
	// fmt.Printf("getFieldByName val %v \n", val)
 
	if val.Kind() != reflect.Struct {
		fmt.Printf("getFieldByName input is not a struct")
		return nil, fmt.Errorf("getFieldByName input is not a struct")
	}
 
	field := val.FieldByName(fieldName)
	if !field.IsValid() {
		fmt.Printf("getFieldByName field %s not found in the struct", fieldName)
		return nil, fmt.Errorf("getFieldByName field %s not found in the struct", fieldName)
	}
	var inter interface{} = field
	if myStruct, ok := inter.(PositionAdsObj); ok {
		// 如果转换成功，myStruct现在包含MyStruct类型的值
		return myStruct, nil
	} else {
		// 如果转换失败，说明myInterface不包含MyStruct类型的值
		fmt.Println("Conversion failed, myInterface does not contain a PositionAdsObj")
		return nil, fmt.Errorf("Conversion failed, myInterface does not contain a PositionAdsObj")
	}
}
 

注意 getFieldByName 传入的是SearchAdsObj具体类型的实体，而不能是：obj interface{}

func getFieldByName(obj interface{}, fieldName string) (interface{}, error) {

因为反射访问结构体内部字段时候，需要操作的对象是一个实际类型的结构体