英文:
How to Unmarshall to interface type?
问题
我已经构建了一个小例子来说明我想要做的事情：
type Service interface {
Transform()
}
type XYZ struct {
ID string `json:"id"`
}
func (s XYZ) Transform() {}
func main() {
x := "could be anything"
msg := []byte(`{"id": "123"}`)
var msgS Service
switch x {
case "could be anything":
msgS = XYZ{}
break
case "could be something else":
// another type that implements Transform()
break
}
err := json.Unmarshal(msg, &msgS)
if err != nil {
fmt.Println(err)
}
// msgS.Transform()
}
这会返回一个错误：
json: cannot unmarshal object into Go value of type main.Service
基本上，我需要根据x可能包含的内容来灵活处理。如果我将msgS实例化为实际实现Transform()的类型，一切都按预期工作。
我意识到我可能需要重新考虑整个实现 - 欢迎任何想法！
英文:
I have constructed a small example of what I am trying to do:
type Service interface {
Transform()
}
type XYZ struct {
ID string `json:"id"`
}
func (s XYZ) Transform() {}
func main() {
x := "could be anything"
msg := []byte(`{"id": "123"}`)
var msgS Service
switch x {
case "could be anything":
msgS = XYZ{}
break
case "could be something else":
// another type that implements Transform()
break
}
err := json.Unmarshal(msg, &msgS)
if err != nil {
fmt.Println(err)
}
// msgS.Transform()
}
This returns an error:
json: cannot unmarshal object into Go value of type main.Service
Essentially, I need to be flexible with whatever x might hold, hence the switch. If I instantitate msgSto the actual type that implements Transform(), all works as expected.
I realise I might need to reconsider my whole implementation - Any ideas would be welcome!
答案1
得分: 2
你应该将其反序列化为具体类型，然后将结果赋值给接口类型。
一个简单的例子：
var service Service
var err error
switch x {
case "something":
var something Something // 这个实现了Service接口
err = json.Unmarshal(data, &something)
service = something
case "something else":
var somethingElse SomethingElse // 这个实现了Service接口
err = json.Unmarshal(data, &somethingElse)
service = somethingElse
// 其他情况...
}
if err != nil {
// 处理错误（可以在此处处理，或者在每个case内部处理，根据需要/喜好而定）
}
// 在这里根据需要使用service
英文:
You should unmarshal to the concrete type and then you can assign the result to the interface type.
A simple example:
var service Service
var err error
switch x {
case "something":
var something Something // this implements Service
err = json.Unmarshal(data, &something)
service = something
case "something else":
var somethingElse SomethingElse // this implements Service
err = json.Unsmarshal(data, &somethingElse)
service = somethingElse
// etc...
}
if err != nil {
// handle error (here or inside of each case if you need/want to)
}
// use service as needed here
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论