用接口干燥我的Go功能

I have the following function:

func (r *Resource) Create(kind string, data io.ReadCloser) (err error) {
  decoder := json.NewDecoder(data)
  r.Kind = kind

  switch kind {
  case "user":
    var user User
    if err = decoder.Decode(&user); err != nil {
      panic(err)
    }

    if err = user.Save(r.Context); err != nil {
      panic(err)
    }

    r.Data = user
    break

  case "space":
    var space Space
    if err = decoder.Decode(&space); err != nil {
      panic(err)
    }

    if err = space.Save(r.Context); err != nil {
      panic(err)
    }

    r.Data = space
    break

  case "room":
    var room Room
    if err = decoder.Decode(&room); err != nil {
      panic(err)
    }

    if err = room.Save(r.Context); err != nil {
      panic(err)
    }

    r.Data = room
    break

  case "element":
    var element Element
    if err = decoder.Decode(&element); err != nil {
      panic(err)
    }

    if err = element.Save(r.Context); err != nil {
      panic(err)
    }

    r.Data = element
    break

  default:
    break
  }
  return
}

As you can see, each case in the switch is identical except for the type of the struct that receives the JSON data.

I suspect that there's an answer in interfaces and type assertion.

EDIT:

I was able to break out the saving part into a separate method, but I still can't figure out a good way to decode the JSON object into the appropriate struct without the switch statement.

func (r *Resource) Create(kind string, data io.ReadCloser) (err error) {
  decoder := json.NewDecoder(data)
  r.Kind = kind

  switch kind {
  case "user":
    var user User
    if err = decoder.Decode(&user); err != nil {
      panic(err)
    }
    r.saveEntity(&user)
    break

  case "space":
    var space Space
    if err = decoder.Decode(&space); err != nil {
      panic(err)
    }
    r.saveEntity(&space)
    break

  case "room":
    var room Room
    if err = decoder.Decode(&room); err != nil {
      panic(err)
    }
    r.saveEntity(&room)
    break

  case "element":
    var element Element
    if err = decoder.Decode(&element); err != nil {
      panic(err)
    }
    r.saveEntity(&element)
    break

  default:
    break
  }
  return
}

func (r *Resource) saveEntity(e Entity) {
  if err := e.Save(r.Context); err != nil {
    panic(err)
  }

  r.Data = e
}

You could move the instantiation to one-line functions and create a mapping which maps the kind to the respective instantiation function. The rest of the code should be re-usable.

Example:

kinds := map[string]func() Entity {
    "user": func() Entity { return &User{} },
    "space": func() Entity { return &Space{} },
    "room": func() Entity { return &Room{} },
}

func Create(kind string) {
    instance := kinds[kind]()

    decoder.Decode(instance)

    saveEntity(instance)
}