Quick Promise - QML Promise Library

benlau

Hi,

In case you are looking for a Promise library that works well with QML , I would like to share my latest open source project with you. Its name is “Quick Promise”. It is a library that provides Promise object in QML way. It comes with a Promise component with signal and property. It could be resolved via a binary expression , another promise object, then trigger your callback by QueuedConnection.

Moreover, it also provides Promise as Javascript object that don’t need to declare in QML way. The API is fully compliant with Promises/A+ specification (Passed all the test cases) and therefore it just works like many other Promise solutions for Javascript application.

Example:


Promise {
    resolveWhen: !someService.running // Once the expression become truth , the onFulfilled signal will be triggered via QueuedConnection
    onFulfilled: { 
    }
}

Promise {
    rejectWhen: timer.onTriggered  // Reject after timeout
   onRejected: {
   }
}

The project link: QuickPromise

Enjoy it.

SGaist

Hi,

You project reminds me of AngularJS. Looks pretty interesting ! Thanks for sharing

benlau

@SGaist Thx

haha, you also reminds me the time when I shift from AngularJS to QML. I tried to understand/write QML in an AngularJS way. Look for a solution of "Transclude" in QML. Assume the item in ListModel support 2 way data binding...

benlau

v1.0.2 has been just released. Now user could resolve a promise by multiple signals and binary expression!

Example

Resolve by multiple signals.


Promise {
    resolveWhen: Q.all([timer.triggered, loader.loaded]);
}

Resolve by signal and binary expression

Promise {
    resolveWhen: Q.all([timer.triggered, promise2]);

    Promise {
        id : promise2
        resolveWhen: image.status === Image.Ready
    }
}

benlau

Quick Promise is now available at qpm.io . You could install latest version (1.0.2) via qpm install com.github.benlau.quickpromise

benlau

v1.0.3 released.

Changes

The resolve parameter to promise generated by Q.all() become an array of results of original promises

cp_mark

This looks pretty promising (pun possibly intended).
I've been looking for something like this to avoid callback hell. However, I need to resolve/reject based off an argument in a signal.

ie.

Item {
        id: obj
        signal done(bool success)
}
Promise {
        id : signalArgPromise
        resolveWhen: obj.done(success === true)
        rejectWhen: obj.done(success === false)
}

Would it be possible to do something like this using your library?

benlau

@cp_mark QML don't support this kind of syntax. So it should either to create signals like success / fail or check the value during the callback function:

onDone: {
  if (success) {
    signalArgPromise.resolve();
  } else {
    signalArgPromise.reject();
  }
}