QuickFlux is a Message Dispatcher / Message Queue solution for Qt/QML. It is also an implementation of Flux Application Architecture (from Facebook). By using this library, users may write their QML application in a Flux way. Their code could be more readable and reusable.
Features
- AppDispatcher
- A singleton Message Dispatcher / Message Queue per QML Engine.
- It guarantees the order of messages are arrived in sequence to listeners (First come first served)
- Write QML application in a Flux way.
- Helper function for C++ code to listen on QML event / obtain QML singleton instance
- Helper components for handling asynchronous sequential workflow.
Generally speaking, you should avoid creating a big QML file. Break down into smaller piece of files is more readable and reusable. But it may not true due to event/signal propagation. Managing code dependence is very troublesome.
Writing QML in a Flux way is a solution for this problem. Using a global AppDispatcher for communication between components. It breaks the dependence and simplify your code by taking out unnecessary signal binding.
This project provides an implementation of dispatcher in QML for user to get started.
Please refer to this article for detail :
Action-Dispatcher Design Pattern for QML — Medium
or
A cartoon guide to Flux — Code Cartoons — Medium
An example program is available for demonstrate how to write QML application in a Flux way quickflux/examples/todo
For user who are already using qpm from qpm.io
- Run
qpm install
$ qpm install com.github.benlau.quickflux
- Include vendor/vendor.pri in your .pro file
You may skip this step if you are already using qpm.
include(vendor/vendor.pri)
- Add import statement in your QML file
import QuickFlux 1.0
-
Clone this repository or download release to a folder within your source tree.
-
Add this line to your profile file(.pro):
include(quickflux/quickflux.pri) # You should modify the path by yourself
-
Add import statement in your QML file
import QuickFlux 1.0
There are few example programs available at examples folder:
Why use AppDispatcher instead of listening from AppActions directly?
Example:
import QtQuick 2.2
pragma Singleton
QtObject {
signal openItem(string id);
signal removeItem(string id);
}
ANS: Of course you could implement in this way. However, AppDispatcher offer two advantages over that approach:
- Avoid out-of-order message processing.
Signal emission in QML is , in fact, on last come, first served basis. If you emit another signal while in a callback, it will process the latest signal immediately. That means the sequence of message processing will be out-of-order. However, AppDispatcher will not dispatch a new message while in a callback. It will be placed in a queue until all of the listeners received the current message. So that the order of message is guaranteed to arrive in sequence.
- Setup dependence between stores.
Quoted from Why We Need a Dispatcher:
As an application grows, dependencies across different stores are a near certainty.
Store A will inevitably need Store B to update itself first, so that Store A can know
how to update itself. We need the dispatcher to be able to invoke the callback for Store B,
and finish that callback, before moving forward with Store A. To declaratively assert this
dependency, a store needs to be able to say to the dispatcher, "I need to wait for Store B
to finish processing this action." The dispatcher provides this functionality through its
waitFor() method."
AppListener supports “waitFor” property to setup dependencies on another AppListener. It won't process the emitted signal and wait until the other listener received the message. Therefore, you could control the order of message delivary.
- benlau/quickpromise - Promise library for QML
- benlau/quickcross - QML Cross Platform Utility Library
- benlau/qsyncable - Synchronize data between models
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