Need help with Promises

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Hey guys. Is this the right channel to ask for help? I recently started to write a plugin to integrate the Vorwerk Kobold VR200 into pimatic based on node-kobold. I already have a JS CLI client written that works, so now I’m trying to mold it into the pimatic ecosystem & put it in coffee script.

The one point that I’m currently stuck at: Promises. Probably the classiest problem one would solve with promises: First authenticate with the server, then ask for details and give instructions.

my code so far

The problem: The connection works. The last thing that gets logged upon start up is “successfully connected to robot”, so the promise should resolve and the “connected” warning should be triggered in the .then() part… but that doesn’t happen.

What am I missing?

Happy to provide more context if needed & thanks in advance for having a look!

@marius said in Need help with Promises:

What am I missing?

Hi Marius.

Nice work! It’ll be easier to collaborate on this if you set up a github project for this.

Looking at your code there is just a minor, but important thing missing. While you can omit brackets with function calls which include parameters you cannot do so without parameters, i.e you need to write reject() and resolve() as just writing reject, for example, will return the function without calling it at this point. Same applies for your getRob() method. For the reject case my suggestion is to pass the error along, so that you handle it eventually later on. At the point where you invoke connect() you should also have a catch block as otherwise you may see unhandled exceptions if the authorization fails for some reason.

Note beyond, it is also possible to automatically promisify callback interfaces, like node-kobold. See http://bluebirdjs.com/docs/api/promisification.html for info.

    connect: () =>
      return new Promise( (resolve, reject) =>
        @client.authorize(@config.email, @config.password, false, (error) ->
          if error
            env.logger.warn error
            reject(error)
          else
            env.logger.info("successfully connected to robot")
            resolve()
        )
      )
    getRob: () =>
      env.logger.info("getrob 0")
      return new Promise( (resolve, reject) =>
        env.logger.info("getrob 1")
        @client.getRobots( (error, robots) =>
          env.logger.info("getrob 2")
          if error
            env.logger.warn error
            reject(error)
          else
            env.logger.info("getrob 3")
            if robots.length
              @robot = robots[@config.robotno]
              env.logger.info("robot selected")
              resolve()
            else
              env.logger.warn "no robot found"
              reject(new Error("no robot found")
        )
      )


    constructor: (@config) ->
      @name = @config.name
      @id = @config.id

      @client = new libKobold.Client()

      @connect().then( () =>
        env.logger.warn "connected"
      )
      .catch( (error) =>
        env.logger.error '' + error
      )

Oh boy. That really wasn’t complicated… But I wouldn’t have found that myself, I’m fairly new to coffee script. Thanks for the quick help!

Yes, once I have the first version that can be implemented and does at least something, I’ll add it to github for collaboration and npm & pimatic for usage. I hope there are more Kobold users in the pimatic community

@marius You’re welcome!

Note, you can the coffee-script tool to obtain the Javascript (JS) compilation output in a file. This was a great help for me in the beginning as the generated JS is fairly easy to read. Some IDE like InteliJ will do that for you on the fly btw.

In case you’re using the coffee-script tool, make sure the JS files do not get accidentially checked into your Github project, e.g. set a .gitignore rule for that. Oterwise, pimatic may pickup the JS files rather than generating it from CS on the fly.