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| 1 // Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file | |
| 2 // for details. All rights reserved. Use of this source code is governed by a | |
| 3 // BSD-style license that can be found in the LICENSE file. | |
| 4 | |
| 5 library observe.src.change_notifier; | |
| 6 | |
| 7 import 'dart:async'; | |
| 8 import 'dart:collection' show UnmodifiableListView; | |
| 9 import 'package:observe/observe.dart'; | |
| 10 import 'package:observe/src/observable.dart' show notifyPropertyChangeHelper; | |
| 11 | |
| 12 /// Mixin and base class for implementing an [Observable] object that performs | |
| 13 /// its own change notifications, and does not need to be considered by | |
| 14 /// [Observable.dirtyCheck]. | |
| 15 /// | |
| 16 /// When a field, property, or indexable item is changed, a derived class should | |
| 17 /// call [notifyPropertyChange]. See that method for an example. | |
| 18 abstract class ChangeNotifier implements Observable { | |
| 19 StreamController _changes; | |
| 20 List<ChangeRecord> _records; | |
| 21 | |
| 22 Stream<List<ChangeRecord>> get changes { | |
| 23 if (_changes == null) { | |
| 24 _changes = new StreamController.broadcast(sync: true, | |
| 25 onListen: observed, onCancel: unobserved); | |
| 26 } | |
| 27 return _changes.stream; | |
| 28 } | |
| 29 | |
| 30 // TODO(jmesserly): should these be public? They're useful lifecycle methods | |
| 31 // for subclasses. Ideally they'd be protected. | |
| 32 /// Override this method to be called when the [changes] are first observed. | |
| 33 void observed() {} | |
| 34 | |
| 35 /// Override this method to be called when the [changes] are no longer being | |
| 36 /// observed. | |
| 37 void unobserved() { | |
| 38 // Free some memory | |
| 39 _changes = null; | |
| 40 } | |
| 41 | |
| 42 bool deliverChanges() { | |
| 43 var records = _records; | |
| 44 _records = null; | |
| 45 if (hasObservers && records != null) { | |
| 46 _changes.add(new UnmodifiableListView<ChangeRecord>(records)); | |
| 47 return true; | |
| 48 } | |
| 49 return false; | |
| 50 } | |
| 51 | |
| 52 /// True if this object has any observers, and should call | |
| 53 /// [notifyPropertyChange] for changes. | |
| 54 bool get hasObservers => _changes != null && _changes.hasListener; | |
| 55 | |
| 56 /// Notify that the field [name] of this object has been changed. | |
| 57 /// | |
| 58 /// The [oldValue] and [newValue] are also recorded. If the two values are | |
| 59 /// equal, no change will be recorded. | |
| 60 /// | |
| 61 /// For convenience this returns [newValue]. This makes it easy to use in a | |
| 62 /// setter: | |
| 63 /// | |
| 64 /// var _myField; | |
| 65 /// @reflectable get myField => _myField; | |
| 66 /// @reflectable set myField(value) { | |
| 67 /// _myField = notifyPropertyChange(#myField, _myField, value); | |
| 68 /// } | |
| 69 notifyPropertyChange(Symbol field, Object oldValue, Object newValue) | |
| 70 => notifyPropertyChangeHelper(this, field, oldValue, newValue); | |
| 71 | |
| 72 void notifyChange(ChangeRecord record) { | |
| 73 if (!hasObservers) return; | |
| 74 | |
| 75 if (_records == null) { | |
| 76 _records = []; | |
| 77 scheduleMicrotask(deliverChanges); | |
| 78 } | |
| 79 _records.add(record); | |
| 80 } | |
| 81 } | |
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Chromium Code Reviews
Issue 2989763002:
Update charted to 0.4.8 and roll (Closed)
