如何在 Go 中将 JSON 解组为 interface{}？
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How to unmarshal JSON into interface{} in Go?
提问by Shanicky_C
I'm a newbie in Go and now I have a problem. I have a type called Message, it is a struct like this:
我是 Go 的新手，现在遇到了问题。我有一个名为 Message 的类型，它是一个这样的结构：
type Message struct {
Cmd string `json:"cmd"`
Data interface{} `json:"data"`
}
I also have a type called CreateMessage like this:
我还有一个叫做 CreateMessage 的类型，如下所示：
type CreateMessage struct {
Conf map[string]int `json:"conf"`
Info map[string]int `json:"info"`
}
And I have a JSON string like {"cmd":"create","data":{"conf":{"a":1},"info":{"b":2}}}.
我有一个像{"cmd":"create","data":{"conf":{"a":1},"info":{"b":2}}}.
When I use json.Unmarshalto decode that into a Message variable, the answer is {Cmd:create Data:map[conf:map[a:1] info:map[b:2]]}.
当我用来json.Unmarshal将其解码为 Message 变量时，答案是{Cmd:create Data:map[conf:map[a:1] info:map[b:2]]}.
So could I decode the JSON into a Message struct and change its Data's interface{} to type CreateMessage according to the Cmd?
那么我可以将 JSON 解码为 Message 结构并根据 Cmd 更改其数据接口{}以键入 CreateMessage 吗？
I tried to convert Data directly into type CreateMessage but the complier told me that Data is a map[sting]interface{} type.
我尝试将 Data 直接转换为 CreateMessage 类型，但编译器告诉我 Data 是一种 map[sting]interface{} 类型。
回答by Cerise Limón
Define a struct type for the fixed part of the message with a json.RawMessagefield to capture the variant part of the message. Define struct types for each of the variant types and decode to them based on the the command.
使用json.RawMessage字段为消息的固定部分定义结构类型以捕获消息的变体部分。为每个变体类型定义结构类型，并根据命令对其进行解码。
type Message struct {
Cmd string `json:"cmd"`
Data json.RawMessage
}
type CreateMessage struct {
Conf map[string]int `json:"conf"`
Info map[string]int `json:"info"`
}
func main() {
var m Message
if err := json.Unmarshal(data, &m); err != nil {
log.Fatal(err)
}
switch m.Cmd {
case "create":
var cm CreateMessage
if err := json.Unmarshal([]byte(m.Data), &cm); err != nil {
log.Fatal(err)
}
fmt.Println(m.Cmd, cm.Conf, cm.Info)
default:
log.Fatal("bad command")
}
}
