在切片中解组2个不同的结构

Question

My input json data is this (cannot be changed, from an external resource):

[{
   "Url": "test.url",
   "Name": "testname"
},{ 
   "FormName": "Test - 2018",
   "FormNumber": 43,
   "FormSlug": "test-2018"
}]

I have two structs that will always match the data within the array:

type UrlData struct{
  "Url"  string `json:Url` 
  "Name" string `json:Name` 
}

type FormData struct{
  "FormName"  string `json:FormName` 
  "FormNumber" string `json:FormNumber` 
  "FormSlug" string `json:FormSlug`
}

Obviously the code below will not work, but is it possible at the top level (or otherwise) to declare something like this:

type ParallelData [
 urlData UrlData
 formData FormData
]

Answer 1

Use a two step process for unmarshaling. First, unmarshal a list of arbitrary JSON, then unmarshal the first and second element of that list into their respective types.

You can implement that logic in a method called UnmarshalJSON, thus implementing the json.Unmarshaler interface. This will give you the compound type you are looking for:

type ParallelData struct {
    UrlData  UrlData
    FormData FormData
}

// UnmarshalJSON implements json.Unmarshaler.
func (p *ParallelData) UnmarshalJSON(b []byte) error {
    var records []json.RawMessage
    if err := json.Unmarshal(b, &records); err != nil {
        return err
    }

    if len(records) < 2 {
        return errors.New("Short JSON array")
    }

    if err := json.Unmarshal(records[0], &p.UrlData); err != nil {
        return err
    }

    if err := json.Unmarshal(records[1], &p.FormData); err != nil {
        return err
    }

    return nil
}

Try it on the playground: https://play.golang.org/p/QMn_rbJj-P-