[英]How to Unmarshal JSON into an interface in Go
I am trying to simultaneously unmarshal and strip fields from a number of different JSON responses into appropriate Go structs. 我试图同时解组和剥离来自许多不同的JSON响应的字段到适当的Go结构。 To do this, I created a Wrappable interface that defines the Unwrap method (which strips the appropriate fields) and pass that interface to the code that unmarshals and unwraps.
为此,我创建了一个Wrappable接口,该接口定义Unwrap方法(剥离相应的字段),并将该接口传递给解组和解包的代码。 It looks like the following example (also at http://play.golang.org/p/fUGveHwiz9 ):
看起来像以下示例(也位于http://play.golang.org/p/fUGveHwiz9 ):
package main
import (
"encoding/json"
"fmt"
)
type Data struct {
A string `json:"a"`
B string `json:"b"`
}
type DataWrapper struct {
Elements []Data `json:"elems"`
}
type Wrapper interface {
Unwrap() []interface{}
}
func (dw DataWrapper) Unwrap() []interface{} {
result := make([]interface{}, len(dw.Elements))
for i := range dw.Elements {
result[i] = dw.Elements[i]
}
return result
}
func unmarshalAndUnwrap(data []byte, wrapper Wrapper) []interface{} {
err := json.Unmarshal(data, &wrapper)
if err != nil {
panic(err)
}
return wrapper.Unwrap()
}
func main() {
data := `{"elems": [{"a": "data", "b": "data"}, {"a": "data", "b": "data"}]}`
res := unmarshalAndUnwrap([]byte(data), DataWrapper{})
fmt.Println(res)
}
However, when I run the code, Go panics with the following error: 但是,当我运行代码时,出现以下错误导致出现紧急情况:
panic: json: cannot unmarshal object into Go value of type main.Wrapper
It seems the unmarshaller doesn't want to be passed a pointer to an interface. 似乎解组器不想传递给接口的指针。 I am somewhat surprised by this given that I can get at the underlying type and fields using the reflect package within the unmarshalAndUnwrap method.
鉴于我可以使用unmarshalAndUnwrap方法中的reflect包了解底层类型和字段,因此对此我感到有些惊讶。 Can anyone provide insight into this problem and how I might work around it?
谁能提供对此问题的见解以及我如何解决该问题?
As you stated, passing a non-pointer fails. 如您所述,传递非指针失败。 Why are you trying to do this anyway?
您为何仍要尝试这样做?
Replace 更换
res := unmarshalAndUnwrap([]byte(data), DataWrapper{})
by 通过
res := unmarshalAndUnwrap([]byte(data), &DataWrapper{})
It should do the trick and it avoid unnecessary copy. 它可以解决问题,避免不必要的复制。
This error should help you understand: http://play.golang.org/p/jXxCxPQDOw 此错误应该可以帮助您了解: http : //play.golang.org/p/jXxCxPQDOw
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