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Event Bus framework for Delphi

This is a independent fork from Daniele Spinetti's DEB implementation, supporting the latest Delphi version only. Please use Daniele's DEB for your production software development, though you are welcome to use this fork if you like.

Delphi Event Bus (for short DEB) is a publish/subscribe Event Bus framework for the Delphi platform.

DEB is designed to decouple different parts/layers of your application while still allowing them to communicate efficiently. It was inspired by EventBus framework for the Android platform.

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Features

  • Easy and clean: DelphiEventBus is super easy to learn and use because it respects KISS and "Convention over configuration" design principles. By using default TEventBus instance, you can start immediately to delivery and receive events
  • Designed to decouple different parts/layers of your application
  • Event Driven
  • Attributes based API: Simply put the Subscribe attribute on your subscriber method you are able to receive a specific event
  • Support different delivery mode: Specifying the TThreadMode in Subscribe attribute, you can choose to delivery the event in the Main Thread or in a Background ones, regardless where an event was posted. The EventBus will manage Thread synchronization
  • Unit Tested
  • Thread Safe

Sample Code

Events

1.Define events:

IEvent = interface(IInterface)
['{3522E1C5-547F-4AB6-A799-5B3D3574D2FA}']
// additional information here
end;

2.Prepare subscribers:

  • Declare your subscribing method:
[Subscribe]
procedure OnEvent(AEvent: IAnyTypeOfEvent);
begin
  // manage the event 	
end;
  • Register your subscriber:
GlobalEventBus.RegisterSubscriberForEvents(Self);

3.Post events:

GlobalEventBus.post(LEvent);

Channels

1.Define channel:

const MY_CHANNEL = 'MYCHANNEL'

2.Prepare subscribers:

  • Declare your subscribing method:
[Channel(MY_CHANNEL)]
procedure OnMessage(AMsg: string);
begin
  // manage the message 	
end;
  • Register your subscriber:
GlobalEventBus.RegisterSubscriberForChannels(Self);

3.Post event on channel:

GlobalEventBus.post(MY_CHANNEL, 'My Message');

Support

  • DEB is a 100% ObjectPascal framework so it works on VCL and Firemonkey
  • It works with latest version Alexandria

Release Notes

DEB 2.1

  • NEW! Introduced dedicated thread pool for DEB threading

DEB 2.0

  • NEW! Added new Interface based mechanism to declare and handle events!
  • NEW! Added channels for simple string-based events
  • NEW! Removed internal CloneEvent because now events are interface based!

Breaking Changes

  • A subscriber method can only have 1 parameter that is an IInterface or descendants
  • EventBus.Post method can accept only an interface as parameter now

License

Copyright 2016-2022 Daniele Spinetti

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Last edited by Wuping Xin (@wxinix). May 31, 2022.