Week 5 Conversations with DynamoDB - TypeError: 'NoneType' object is not subscriptable

• Debug log: https://github.com/CloudWest2023/aws-bootcamp-cruddur-2023/commit/dd3f9692b4ebeb0750c83fbd2079c4ace537ca1d

The problem I had with this unsubscriptable Nonetype error was that the data was getting lost somewhere. So no matter how many times I click on the individual conversation groups, the data is not coming back so I couldn't see the conversation on the right column.

Every time I click on the conversation group (either Andrew Brown or Worf), it runs the following code in the backend:

# backend-flask/app.py 

@app.route("/api/messages/<string:message_group_uuid>", methods=['GET'])
def data_messages(message_group_uuid): 
  access_token = jwttv.extract_access_token(request.headers)

  try:
    claims = jwttv.verify(access_token)
    cognito_user_id = claims['sub']
    model = Messages.run(
      cognito_user_id = cognito_user_id,
      message_group_uuid = message_group_uuid
    )

The model is created by the function Message.run, the only function of the class Messages in messages.py. As it turns out, model was missing in the return statement.

# backend-flask/services/messages.py

class Messages:
  def run(message_group_uuid, cognito_user_id):
    printh("Messages.run() ...")
    model = {
      'errors': None,
      'data': None
    }

    sql = db.template('users', 'uuid_from_cognito_user_id')
    current_user_uuid = db.query_value(sql, { 
        'cognito_user_id': cognito_user_id 
    })

    ddb_client = ddb.client()
    data = ddb.list_messages(ddb_client, message_group_uuid)
    model['data'] = data
    return              #  <-------- return should return model

Modifying the return line to return model neatly solved the problem.

Simple enough? Yes, you just have to know where to look 👀.