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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.compound_path_observer; | |
| 6 | |
| 7 import 'dart:async'; | |
| 8 import 'package:observe/observe.dart'; | |
| 9 | |
| 10 /** | |
| 11 * CompoundPathObserver is an object which knows how to listen to multiple path | |
| 12 * values (registered via [addPath]) and invoke a function when one or more | |
| 13 * of the values have changed. The result of this function will be set into the | |
| 14 * [value] property. When any value has changed, all current values are provided | |
| 15 * to the function in the single `values` argument. | |
| 16 * | |
| 17 * For example: | |
| 18 * | |
| 19 * var binding = new CompoundPathObserver(computeValue: (values) { | |
| 20 * var combinedValue; | |
| 21 * // compute combinedValue based on the current values which are provided | |
| 22 * return combinedValue; | |
| 23 * }); | |
| 24 * binding.addPath(obj1, path1); | |
| 25 * binding.addPath(obj2, path2); | |
| 26 * //... | |
| 27 * binding.addPath(objN, pathN); | |
| 28 */ | |
| 29 // TODO(jmesserly): this isn't a full port of CompoundPathObserver. It is only | |
| 30 // what was needed for TemplateBinding. | |
| 31 class CompoundPathObserver extends ChangeNotifier { | |
| 32 List<PathObserver> _observers = []; | |
| 33 List<StreamSubscription> _subs = []; | |
| 34 Object _value; // the last computed value | |
| 35 | |
| 36 // TODO(jmesserly): this is public in observe.js | |
| 37 final Function _computeValue; | |
| 38 | |
| 39 bool _started = false; | |
| 40 | |
| 41 /** True if [start] has been called, otherwise false. */ | |
| 42 bool get started => _started; | |
| 43 | |
| 44 bool _scheduled = false; | |
| 45 | |
| 46 /** | |
| 47 * Creates a new observer, optionally proving the [computeValue] function | |
| 48 * for computing the value. You can also set [schedule] to true if you plan | |
| 49 * to invoke [resolve] manually after initial construction of the binding. | |
| 50 */ | |
| 51 CompoundPathObserver({computeValue(List values)}) | |
| 52 : _computeValue = computeValue; | |
| 53 | |
| 54 int get length => _observers.length; | |
| 55 | |
| 56 @reflectable get value => _value; | |
| 57 | |
| 58 void addPath(model, String path) { | |
| 59 if (_started) { | |
| 60 throw new StateError('Cannot add more paths once started.'); | |
| 61 } | |
| 62 | |
| 63 _observers.add(new PathObserver(model, path)); | |
| 64 } | |
| 65 | |
| 66 void start() { | |
| 67 if (_started) return; | |
| 68 _started = true; | |
| 69 | |
| 70 final scheduleResolve = _scheduleResolve; | |
| 71 for (var observer in _observers) { | |
| 72 _subs.add(observer.changes.listen(scheduleResolve)); | |
| 73 } | |
| 74 _resolve(); | |
| 75 } | |
| 76 | |
| 77 // TODO(rafaelw): Is this the right processing model? | |
| 78 // TODO(rafaelw): Consider having a seperate ChangeSummary for | |
| 79 // CompoundBindings so to excess dirtyChecks. | |
| 80 void _scheduleResolve(_) { | |
| 81 if (_scheduled) return; | |
| 82 _scheduled = true; | |
| 83 scheduleMicrotask(_resolve); | |
| 84 } | |
| 85 | |
| 86 void _resolve() { | |
| 87 _scheduled = false; | |
| 88 if (_observers.isEmpty) return; | |
| 89 var newValue = _observers.map((o) => o.value).toList(); | |
| 90 if (_computeValue != null) newValue = _computeValue(newValue); | |
| 91 _value = notifyPropertyChange(#value, _value, newValue); | |
| 92 } | |
| 93 | |
| 94 /** | |
| 95 * Closes the observer. | |
| 96 * | |
| 97 * This happens automatically if the [value] property is no longer observed, | |
| 98 * but this can also be called explicitly. | |
| 99 */ | |
| 100 void close() { | |
| 101 if (_observers.isEmpty) return; | |
| 102 | |
| 103 if (_started) { | |
| 104 for (StreamSubscription sub in _subs) { | |
| 105 sub.cancel(); | |
| 106 } | |
| 107 } | |
| 108 _observers.clear(); | |
| 109 _subs.clear(); | |
| 110 _value = null; | |
| 111 } | |
| 112 | |
| 113 observed() => start(); | |
| 114 unobserved() => close(); | |
| 115 } | |
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Chromium Code Reviews
Issue 132403010:
big update to observe, template_binding, polymer (Closed)
Base URL: https://dart.googlecode.com/svn/branches/bleeding_edge/dart