async_command_handling.md

Async command handling

In most case, we could simply send a http request to execute command, and get result from the http response. However, this is not a good way for time-consuming command, such as take_picture , stop_record and so on.

Pro Camera API provide a way to execute command asynchronously. Take take_picture command as an example, the http response looks like this

{
  "name":"camera._takePicture",
  "state":"done",
  "sequence":int
}

There is no result in the response. Instead, there is a sequence value. The sequence acts as an asynchronous task token, which identifis this take_picture command and could be used to get the actual result later.

In State polling, we introduced the response of state command, where there is a _idRes atrribute. The value of _idRes attributes is an array of such sequence whose corresponding async task has finished executing. So once the sequence of take_picture command is listed in _idRes , we could then get the actual result of the command.

get_result command

get_result command is designed to get actual result of async command.

Request

{
  "name":"camera._getResult",
  "parameters": {
    "list_ids":[int] //array of sequence you want to get result.
  }
}

Response

{
  "name":"camera._getResult",
  "results":{
    "res_array":[
      {
        "id":int, //the sequence id
        "name":string, //name of the async command
        "results":{ //the sync command results
          "state":"done",
          ...
        }
      }
    ]
  }
}

eg. If we send an get_result command with a take_picture sequence id. The response looks like this

{
  "name":"camera._getResult",
  "results":{//results of get_result command
    "res_array":[
      {
        "id":int, //the sequence stop_record command
        "name":"camera._stopRecording", //name of the async command
        "results":{ //the origin command response
          "state":"done",
          "results": {//the origin command results
            "_picUrl":string
          }
        }
      }
    ]
  }
}