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Unified event handling model #1873

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DartBot opened this issue Feb 27, 2012 · 17 comments
Closed

Unified event handling model #1873

DartBot opened this issue Feb 27, 2012 · 17 comments
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area-library type-enhancement A request for a change that isn't a bug

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@DartBot
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DartBot commented Feb 27, 2012

This issue was originally filed by @seaneagan


Dart needs a unified approach to handling asynchronous events including:

ui events (dart:html)
async operation completion (Future/Completer in dart:core)
Message sending and receiving (dart:isolates)

Strawman proposal at:

https://docs.google.com/document/d/17crOxOmR5AYwultXbNcfdbvD4ACBw5a9QbvO90FVgtk/edit

@iposva-google
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cc @sigmundch.
cc @madsager.
cc @vsmenon.
cc @kasperl.
Removed Type-Defect label.
Added Type-Enhancement, Area-Library, Triaged labels.

@sigmundch
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Added Isolates label.

@sethladd
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Comments from a recent Code Lab:

"Contrast: WebSocketConnection "ws.onClosed=(int, String){}" syntax is very different from the WebSocket "ws.on.close.add((e){})" syntax. That's weird and surprising."

@nex3
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nex3 commented Jul 25, 2012

The events in dart:io should also be unified in this way.

It would be good if whatever event model we ended up using supported multiple listeners per event. See also issue #4202.

@DartBot
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DartBot commented Jul 26, 2012

This comment was originally written by kaisellgren@gmail.com


I just had a need for firing events in my classes to let other code know about "events". I also ended up writing an ObservableList class that utilizes my event library, but I'd really like to see native support for events Dart so that any class can just fire an event, etc. This could be implemented on a very base class or be a mixin called Observable that you just mix into whatever classes you want to.

@DartBot
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DartBot commented Aug 10, 2012

This comment was originally written by rtimon...@gmail.com


http://ricardo.cc/2012/08/09/Its-time-for-a-native-EventEmitter.html

Explains nicely in what kind of mess you can end up with if you don't provide native language event support, or a canonical complete implementation in the base library.

@sigmundch
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Added Library-Isolates label.

@sigmundch
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Removed Isolates label.

@alan-knight
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Changed the title to: "Unified event handling model".

@DartBot
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DartBot commented Nov 2, 2012

This comment was originally written by prujo...@gmail.com


Since events, messages, async operations, network I/O, iterators, etc. can all be considered either terminating or non-terminating sequences of data, I propose that they all be unified under the same Observable model.

Examples:

Observable
  .fromList([1,2,3,4])
  .observe((next) => print('$next'), () => print('finished!'));

Observable
  .fromEvent(element.on.click)
  .observe((next) => print('you clicked me'), (){}, (e) => print('error!'));

// composability
Observable
  .fromEvent(element.on.click)
  .throttle(50) // only pass data if 50ms has passed
  .transform((event) => 'you clicked something')
  .observe((next) => print(next));

// combinators
Observable
  .merge([observer1, observer2, observer3])
  .observe((next) => print('merged data from list of observers: $next'));

Benefits:

  • unified
  • familiar
  • composable
  • extensible (combinators, parallel operators later...)

See http://pub.dartlang.org/packages/reactive as a reference project.

@dgrove
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dgrove commented Jan 11, 2013

Added Library-Isolate label.

@dgrove
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dgrove commented Jan 11, 2013

Removed Library-Isolates label.

@DartBot
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DartBot commented Jan 31, 2013

This comment was originally written by jon...@gmail.com


I agree with this change request. I want my class to be able to alert other classes that some state has changed.

@DartBot
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DartBot commented Jan 31, 2013

This comment was originally written by er...@codesmithtools.com


The new Stream API in Dart is going to be their unified eventing pattern. It still has some rough edges, but it is completely composable and gives all the desired features listed in this issue. I just created a package that makes exposing custom events as streams really easy. I am guessing that the Dart team will have similar functionality built into the SDK soon. Here is my pub package:

http://pub.dartlang.org/packages/event_stream

Here is an example of how to create a custom event:

class ClassWithEvents implements NotifyPropertyChanged {
  String _someProperty;

  final EventStream<PropertyChangedEventArgs> _onPropertyChangedEvent = new EventStream<PropertyChangedEventArgs>();
  Stream<PropertyChangedEventArgs> get onPropertyChanged => _onPropertyChangedEvent.stream;

  final EventStream _onClosedEvent = new EventStream();
  Stream get onClosed => _onClosedEvent.stream;

  String get someProperty => _someProperty;
  set someProperty(String value) {
    _onPropertyChangedEvent.signal(new PropertyChangedEventArgs('someProperty', value));
    _someProperty = value;
  }

  close() {
    _onClosedEvent.signal();
  }
}

main() {
  var c = new ClassWithEvents();
  c.onPropertyChanged.listen((PropertyChangedEventArgs<String> args) => print('changed: name=${args.propertyName} value=${args.value}'));
  c.onClosed.listen((_) => print('closed'));
  c.someProperty = "test";
  c.close();
}

@DartBot
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DartBot commented Jan 31, 2013

This comment was originally written by jonapu...@gmail.com


Just checked out the event_stream package. It definitely helps simplify things.

@sethladd
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sethladd commented Mar 5, 2013

Hi Florian, I think we can close this, yes?


cc @floitschG.
Removed Library-Isolate label.

@floitschG
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Yes.


Added Fixed label.

@kevmoo kevmoo added type-enhancement A request for a change that isn't a bug and removed type-enhancement labels Mar 1, 2016
copybara-service bot pushed a commit that referenced this issue Jan 31, 2023
…g, mockito, package_config, shelf, string_scanner, test, webdev

Revisions updated by `dart tools/rev_sdk_deps.dart`.

async (https://github.com/dart-lang/async/compare/f700e9a..f700e9a):
  f700e9a  2023-01-27  Devon Carew  blast_repo fixes (#231)

characters (https://github.com/dart-lang/characters/compare/4526aa8..4526aa8):
  4526aa8  2023-01-30  Lasse R.H. Nielsen  Update tables to Unicode 15.0. (#71)

collection (https://github.com/dart-lang/collection/compare/a566328..a566328):
  a566328  2023-01-26  Devon Carew  add a publish script; prep to publish (#267)

dartdoc (https://github.com/dart-lang/dartdoc/compare/bc7bdc4..bc7bdc4):
  bc7bdc44  2023-01-30  dependabot[bot]  Bump js from 0.6.5 to 0.6.7 (#3310)

json_rpc_2 (https://github.com/dart-lang/json_rpc_2/compare/e73c4ad..e73c4ad):
  e73c4ad  2023-01-26  Devon Carew  blast_repo fixes (#89)

logging (https://github.com/dart-lang/logging/compare/399100a..399100a):
  399100a  2023-01-26  Devon Carew  add a publish script; prep to publish 1.1.1 (#128)

mockito (https://github.com/dart-lang/mockito/compare/d2a8df1..d2a8df1):
  d2a8df1  2023-01-30  Kevin Moore  Latest build_web_compilers, move to pkg:lints, fix breaks (#605)
  13340b5  2023-01-30  dependabot[bot]  Bump dart-lang/setup-dart from 1.3 to 1.4 (#600)

package_config (https://github.com/dart-lang/package_config/compare/3fe81c4..3fe81c4):
  3fe81c4  2023-01-30  Kevin Moore  Support latest pkg:build_web_compilers, lints. Update min SDK (#129)

shelf (https://github.com/dart-lang/shelf/compare/8fca9d9..8fca9d9):
  8fca9d9  2023-01-26  Devon Carew  blast_repo fixes (#326)

string_scanner (https://github.com/dart-lang/string_scanner/compare/29e471e..29e471e):
  29e471e  2023-01-30  dependabot[bot]  Bump dart-lang/setup-dart from 1.3 to 1.4 (#53)

test (https://github.com/dart-lang/test/compare/cec47c1..cec47c1):
  cec47c1c  2023-01-27  Nate Bosch  Add missing pub requirements (#1878)
  c99d455e  2023-01-27  Nate Bosch  Prepare to publish (#1877)
  0e7ec6a7  2023-01-27  Nate Bosch  Rename `Check` to `Subject` (#1875)
  78382731  2023-01-27  Nate Bosch  Add String.matches condition (#1874)
  26e0e87b  2023-01-27  Nate Bosch  Add Iterable.containsInOrder condition (#1873)
  c9232d6b  2023-01-27  Nate Bosch  Rename `that` to `which` (#1872)
  457166b3  2023-01-26  Nate Bosch  Add missing dependency on package:lints (#1876)
  193f2a0b  2023-01-26  Nate Bosch  Retry instead of extend timeout for flaky Node tests (#1871)
  7ad9b2c3  2023-01-26  Nate Bosch  Overhaul async matchers (#1868)
  ca254546  2023-01-26  Nate Bosch  Add a withQueue utility (#1870)
  6ae2e5e9  2023-01-26  Nate Bosch  Refactor tests to a new isRejectedBy utility (#1867)
  5aeba66d  2023-01-26  Nate Bosch  Use pubspec_overrides.yaml files (#1869)

webdev (https://github.com/dart-lang/webdev/compare/ce9c581..ce9c581):
  ce9c581  2023-01-29  Anna Gringauze  Validate only needed summaries in expression_compiler_service (#1920)

Change-Id: I3ddb0ddeb3b989f6f9e78cd8aa6327aba5899018
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/280078
Commit-Queue: Devon Carew <devoncarew@google.com>
Auto-Submit: Devon Carew <devoncarew@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
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