Python dict 通过 JSON 和 Rails Action Cable Web 套接字转换为 Ruby 哈希

Question

I am having a hard time passing information properly from a python script to a rails app through web sockets (using Action Cable).

I want to use input information in a python dictionary like this :

message = {
    'command':"subscribe",
    'identifier':{
            'channel': 'RaspChannel',
            'rasp_local_id': '1'
        }
    }

It should then be converted into JSON, go through a web socket set by Action Cable, then parsed into a ruby hash on the server side.

For some reason, I only made it work by sending a plain string through the socket :

'{"command":"subscribe","identifier":"{\\"channel\\":\\"RaspChannel\\", \\"rasp_local_id\\": \\"1\\"}"}'

But I could not make it work by sending json.dumps(message) even though it returned something that looked pretty good to me :

{"command": "subscribe", "identifier": {"channel": "RaspChannel", "rasp_local_id": "1"}}

I suppose action cable protocol uses the classic ruby JSON.parse method on the json string it receives as input, and for some reason, it always throws a parsing error, unless I use the plain string I mentioned above.

However, as I want to make the message more complicated, it would be better if I could make it work with actual Python dictionaries from the beginning.

Any idea on what I am missing ?

Answer 1

After more research, it seems that the issue did not come from either JSON python encoding, ruby decoding, or me misusing any of these methods.

Actually, it would seem that the protocol used by actioncable when receiving messages does not exactly rely on a "classic" JSON, but uses "escaped JSON within the JSON" for the identifier

More on that on the rails github issue here https://github.com/rails/rails/issues/22675