| // Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| library observe.src.auto_observable; |
| |
| import 'dart:async'; |
| import 'dart:collection'; |
| |
| import 'package:observable/observable.dart'; |
| import 'package:smoke/smoke.dart' as smoke; |
| |
| import 'dirty_check.dart' show dirtyCheckObservables, registerObservable; |
| import 'metadata.dart' show ObservableProperty; |
| |
| abstract class AutoObservable implements Observable { |
| /// Performs dirty checking of objects that inherit from [AutoObservable]. |
| /// This scans all observed objects using mirrors and determines if any fields |
| /// have changed. If they have, it delivers the changes for the object. |
| static void dirtyCheck() => dirtyCheckObservables(); |
| |
| StreamController<List<ChangeRecord>> _changes; |
| |
| Map<Symbol, Object> _values; |
| List<ChangeRecord> _records; |
| |
| /// The stream of change records to this object. Records will be delivered |
| /// asynchronously. |
| /// |
| /// [deliverChanges] can be called to force synchronous delivery. |
| @override |
| Stream<List<ChangeRecord>> get changes { |
| if (_changes == null) { |
| _changes = new StreamController.broadcast( |
| sync: true, onListen: observed, onCancel: unobserved); |
| } |
| return _changes.stream; |
| } |
| |
| /// True if this object has any observers, and should call |
| /// [notifyChange] for changes. |
| @override |
| bool get hasObservers => _changes != null && _changes.hasListener; |
| |
| @override |
| void observed() { |
| // Register this object for dirty checking purposes. |
| registerObservable(this); |
| |
| var values = new Map<Symbol, Object>(); |
| |
| // Note: we scan for @observable regardless of whether the base type |
| // actually includes this mixin. While perhaps too inclusive, it lets us |
| // avoid complex logic that walks "with" and "implements" clauses. |
| var queryOptions = new smoke.QueryOptions( |
| includeInherited: true, |
| includeProperties: false, |
| withAnnotations: const [ObservableProperty]); |
| for (var decl in smoke.query(this.runtimeType, queryOptions)) { |
| var name = decl.name; |
| // Note: since this is a field, getting the value shouldn't execute |
| // user code, so we don't need to worry about errors. |
| values[name] = smoke.read(this, name); |
| } |
| |
| _values = values; |
| } |
| |
| /// Release data associated with observation. |
| @override |
| void unobserved() { |
| // Note: we don't need to explicitly unregister from the dirty check list. |
| // This will happen automatically at the next call to dirtyCheck. |
| if (_values != null) { |
| _values = null; |
| } |
| } |
| |
| /// Synchronously deliver pending [changes]. Returns true if any records were |
| /// delivered, otherwise false. |
| // TODO(jmesserly): this is a bit different from the ES Harmony version, which |
| // allows delivery of changes to a particular observer: |
| // http://wiki.ecmascript.org/doku.php?id=harmony:observe#object.deliverchangerecords |
| // |
| // The rationale for that, and for async delivery in general, is the principal |
| // that you shouldn't run code (observers) when it doesn't expect to be run. |
| // If you do that, you risk violating invariants that the code assumes. |
| // |
| // For this reason, we need to match the ES Harmony version. The way we can do |
| // this in Dart is to add a method on StreamSubscription (possibly by |
| // subclassing Stream* types) that immediately delivers records for only |
| // that subscription. Alternatively, we could consider using something other |
| // than Stream to deliver the multicast change records, and provide an |
| // Observable->Stream adapter. |
| // |
| // Also: we should be delivering changes to the observer (subscription) based |
| // on the birth order of the observer. This is for compatibility with ES |
| // Harmony as well as predictability for app developers. |
| @override |
| bool deliverChanges() { |
| if (_values == null || !hasObservers) return false; |
| |
| // Start with manually notified records (computed properties, etc), |
| // then scan all fields for additional changes. |
| var records = _records; |
| _records = null; |
| |
| _values.forEach((name, oldValue) { |
| var newValue = smoke.read(this, name); |
| if (oldValue != newValue) { |
| if (records == null) records = []; |
| records.add(new PropertyChangeRecord(this, name, oldValue, newValue)); |
| _values[name] = newValue; |
| } |
| }); |
| |
| if (records == null) return false; |
| |
| _changes.add(new UnmodifiableListView<ChangeRecord>(records)); |
| return true; |
| } |
| |
| /// Notify that the field [name] of this object has been changed. |
| /// |
| /// The [oldValue] and [newValue] are also recorded. If the two values are |
| /// equal, no change will be recorded. |
| /// |
| /// For convenience this returns [newValue]. |
| @override |
| /*=T*/ notifyPropertyChange/*<T>*/( |
| Symbol field, /*=T*/ oldValue, /*=T*/ newValue) { |
| if (hasObservers && oldValue != newValue) { |
| notifyChange(new PropertyChangeRecord(this, field, oldValue, newValue)); |
| } |
| return newValue; |
| } |
| |
| /// Notify observers of a change. |
| /// |
| /// For most objects [AutoObservable.notifyPropertyChange] is more |
| /// convenient, but collections sometimes deliver other types of changes |
| /// such as a [ListChangeRecord]. |
| /// |
| /// Notes: |
| /// - This is *not* required for fields if you mixin or extend |
| /// [AutoObservable], but you can use it for computed properties. |
| /// - Unlike [Observable] this will not schedule [deliverChanges]; use |
| /// [AutoObservable.dirtyCheck] instead. |
| @override |
| void notifyChange(ChangeRecord record) { |
| if (!hasObservers) return; |
| |
| if (_records == null) _records = []; |
| _records.add(record); |
| } |
| } |