Project: Quick Future - Using QFuture in QML

benlau

Project: Quick Future
Source: https://github.com/benlau/quickfuture

QuickFuture is a QML wrapper of QFuture. It allows user to access and listen from a QFuture object generated by a QObject class. So that QML could respond to the result of a threaded calculation.

Example

import Future 1.0

...

var future = FileActor.read(“tmp.txt”);
// FileActor is a C++ class registered as context property
// QFuture<QString> FileActor::read(const QString&file);
// It is not a part of the library

Future.onFinished(future, function(value) {
  // do something when it is finished.
});

Future.promise(future).then(function(value) {
  // Future.promise creates a promise object by using Quick Promise.
  // It is useful when you have multiple asynchronous tasks pending.
});

...

Installation

qpm install quick.future.pri

Custom Type Registration

By default, QFuture<T> is not a standard type recognized by QML. It must be registered as a QMetaType per template type in order to get rid the error message.

The same rule applies in Quick Future too. Common types are pre-registered already.
For your own custom type, you can register it by:

#include <QFFuture>
Q_DECLARE_METATYPE(QFuture<CustomType>)

...

int main(int argc, char *argv[])
{

...
   QFFuture::registerType<CustomType>();
...

}

Pre-registered data type list: bool, int, qreal, QString, QByteArray, QVariantMap, void.

API

(More API will be added upon request)

Future.isFinished(future)

Returns true if the asynchronous computation represented by this future has finished; otherwise returns false.

Future.onFinished(future, callback)

The callback will be invoked when the watched future finishes.

Future.promise(future)

Create a promise object which will be resolved when the future has finished. It must have QuickPromise installed and setup properly before using this function.

[Moved to Showcase ~kshegunov]

kshegunov

Pretty neat. Thanks for sharing!

Larpon

Thanks for sharing. Your work is much appreciated!

benlau

v1.0.2 has been released!

Critical Changes

The QML package name has been changed from Future to QuickFuture

import QuickFuture 1.0

Custom type registration is done by QuickFuture::registerType instead of QFFuture::registerType

#include <QuickFuture>
Q_DECLARE_METATYPE(QFuture<CustomType>)

...

int main(int argc, char *argv[])
{

...
   QuickFuture::registerType<CustomType>();
...

}

New API

Future.isRunning(future)

Future.isCanceled(future)

Future.onCanceled(future, callback)

Future.result(future)

Future.sync(future, propertyAtFuture, target, propertyAtTarget)

Synchronize a property in future object to target object.

Example:


QtObject {
    id: target1
    property var isRunning
    property var isFinished
}

// Future.sync(future,"isRunning", target1, "isRunning");
// Future.sync(future,"isFinished", target1);

Supported properties: "isRunning", "isCanceled", "isFinished"

benlau

Quick Future v1.0.3 has been released. This version supports a custom type converter for making a QML friendly data structure from QFuture<YourCustomType>. Calling an async function and obtain the result from QML on a C++ class is much easier now.

New Features

Custom Converter function

QuickFuture::registerType() now supports to assign a custom converter for making a QML friendly data structure (e.g QVariantMap) from the custom type. The value could be obtained by using Future.result()


class Actor : public QObject {
Q_OBJECT
public:
  class Reply {
    public:
      int code;
      QString message;
  };
  QFuture<Reply> read(QString source);
}

static void init() {
    QuickFuture::registerType<Actor::Reply>([](Actor::Reply reply) -> QVariant {
        // Optional converter function.
        QVariantMap map;
        map["code"] = reply.code;
        map["message"] = reply.message;
        return map;
    });
}

Q_COREAPP_STARTUP_FUNCTION(init)

var future = Actor.read(source);
....
console.log(Future.result(future)); // Print { code: 0, message: ""} if the reply is empty