event 3.0.1

Create lightweight custom Events, that allow interested subscribers to be notified that something has happened.

Changelog - Event

Version 3.0.0 (2024-08-05)

This version has BREAKING CHANGES

1. Minimum Dart sdk dependency is now 3.4.0
2. An EventArgs instance is created and broadcast automatically if none provided, i.e.

  var e = Event();
    // is equivalent to...
  var e = Event<EventArgs>(); 

3. An Event can have a name specified. Some code might be subscribed to more than one Event, so this lets one know which Event caused the code to run.

  var e = Event("CountUpdatedEvent");
  e.subscribe((args) => print(args.eventName));
  // outputs "null" until the event is broadcast.
  e.broadcast();
  // outputs "CountUpdatedEvent"

4. EventArgs includes two accessible values:- eventName and whenOccurred. Both have a default value of null, and are only populated when the Event is broadcast.

  // Example without Event name
  var e = Event();
  e.subscribe((args) {
    print(args.eventName); // outputs null
    print(args.whenOccurred); // outputs time of broadcast
  };
  e.broadcast();
  
  // Example specifying an Event name
  var e = Event("myEvent");
  e.subscribe((args) {
    print(args.eventName); // outputs "myEvent"
    print(args.whenOccurred); // outputs time of broadcast
  };
  e.broadcast();

5. The WhenWhy EventArg derived class is DEPRECATED and removed. Use the EventArgs whenOccurred property instead.
6. The + and - equivalents to subscribe() and unsubscribe() have been DEPRECATED and removed for simplicity.
7. A custom ArgsError is thrown if an Event is broadcast() without an appropriate argument

  var e = Event<CustomEventArgs>();
  // following throws an ArgsError because broadcast()
  // specifies no CustomEventArgs
  e.broadcast();
  // In this case, the ArgsError message shown would be...
  // "Incorrect args being broadcast - args should be a CustomEventArgs"
  
  // instead, following is correct
  e.broadcast(CustomEventArgs("hello"));

8. A new property genericType has been added to the Event class. Gets the generic type of the Event, e.g.

  var e = Event<Value<int>>();
  assert(e.genericType == Value<int>); 

9. The broadcast() method now returns a bool, indicating if the broadcast had subscribers or not. No subscribers means the broadcast() method is effectively ignored.

  var e = Event();
  // no subscribers
  var hadEffect = e.broadcast();
  assert(hadEffect == false);

10. A syntactical alternative to the broadcast method - notifySubscribers - has been added.

Version 2.1.2 (2022-01-11)

• Small README changes

Version 2.1.0 (2022-01-10)

• Improved README

• ** Breaking Changes **

  • StdEventArgs renamed to WhenWhy to better indicate what the arguments represent.

  var e = Event<WhenWhy>();
  e.broadcast(WhenWhy(description: 'some info'));  

• EventArgs Value and Values now derive from EventArgs rather than WhenWhy (formerly StdEventArgs).

Version 2.0.5 (2021-05-10)

• Fix issue #5. Support the ability to unsubscribeAll within an Event handler.

Version 2.0.4 (2021-05-10)

• GenericEventArg1 and GenericEventArg2 Event argument types renamed to Value and Values. Better reflects common usage. Values supports two values, while Value supports one.

      var e = Event<Value>(); // Event will include a value as an argument
      e.broadcast(Value(39)); // type of the Value inferred to be an int

      // equivalent to 

      var e = Event<Value<int>>();  // type of the Value can also be explicit
      e.broadcast(Value(39));

• Updated tests.

Version 2.0.3 (2021-05-09)

• Make the list of handlers a non-nullable Type that is created lazily using the new 'late' keyword.

This simplifies the code substantially, because no null checks etc. are required.

Version 2.0.2 (2021-05-08)

• Fixed issue #7 https://github.com/aryehof/dart-event/issues/7
• Updated tests.

Version 2.0.1 (2021-03-08)

• Fixed incorrect link to Changelog in README.

Version 2.0.0 (2021-03-08)

• Null safe. (Min SDK version 2.12.0)
• Changes to README content and layout.

Version 1.1.5 (2021-02-28)

• Minor changes to README content and layout.

Version 1.1.4 (2020-06-10)

• Added a subscribeStream method to Event, which supports the broadcasting of Events to a Dart Stream [StreamSink].

  This allows a sequence of broadcast Events to be represented and manipulated as a Dart Stream. The rich range of mechanisms to filter and manipulate Streams become available.

  Remember that the supplied [StreamSink] should be closed when no longer needed.

  // Example
   var e = Event();
   var sc = StreamController();
    
   e.subscribeStream(sc.sink);
   e.broadcast();
    
   sc.stream.listen((e) => print('boom'));
   sc.close();
  

Version 1.1.3 (2020-02-14)

• BasicEventArgs renamed to StdEventArgs for clarity.

Version 1.1.2 (2020-02-09)

• EventArgs changes
  • Added BasicEventArgs as a standard EventArgs derived type. It includes a whenOccurred field that contains the date and time the Event was broadcast, as well as an optional description field.
  • Renamed EventArgs1 and EventArgs2 to GenericEventArgs1 and GenericEventArgs2 respectively, to better indicate their purpose. Both are now derived from BasicEventArgs, meaning that they have whenOccurred and (optional) description fields.
  • Improvements to documentation
• Minor improvements to Event documentation.

Version 1.1.1 (2020-02-03)

• Add new method unsubscribeAll, to unsubscribe all subscribers (handlers).

Version 1.1.0 (2020-01-29)

Breaking Change

The function signature for an Event has been simplified. The sender argument has been removed, leaving only the need to provide an optional argument derived from type EventArgs.

The sender argument was previously intended to be used to provide the source of the Event, or the object in which the Event was declared, to a subscriber. This can be equally well done within an EventArg passed as an argument to a subscriber.

// Before
// subscribe to onValueChanged Event
myCounter.onValueChanged + (sender, args) => print('before');

// Now
// subscribe to onValueChanged Event
myCounter.onValueChanged + (args) => print('after');

Other Breaking Changes

• Renamed addHandler and removeHandler methods to subscribe and unsubscribe respectively.
• Renamed raise methods to broadcast.
• Method broadcastWithSubject removed to reflect to removal of sender described above.
• The count method has been renamed to `subscriberCount'

Other

• Two general purpose EventArg derived classes (EventArgs1 and EventArgs2) have been included, which offers a quick alternative to producing your own custom EventArgs class.

EventArgs1 supports one generic value, while EventArgs2 supports two. Example:-

// EventArgs1 (one value)
var e = Event<EventArgs1<String>>();
e.subscribe((args) => print(args.value));
e.broadcast(EventArgs1('hello'));
// prints hello

// EventArgs2 (two values)
var e = Event<EventArgs2<String, int>>();
e.subscribe((args) => print('${args.value1} - ${args.value2}'));
e.broadcast(EventArgs2('boom', 37));
// prints boom - 37

Version 1.0.3 (2020-01-22)

• Added image of elevator example to README.

Version 1.0.2 (2020-01-22)

• Updated reference to Flutter EventSubscriber in the README.
• Minor documentation improvements

Version 1.0.1 (2020-01-22)

• Documentation improvements and corrections

Version 1.0.0 (2020-01-22)

• Initial release