| // Copyright (c) 2013, 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. |
| |
| part of observe; |
| |
| /** Records a change to an [Observable]. */ |
| abstract class ChangeRecord { |
| // TODO(jmesserly): rename this--it's confusing. Perhaps "matches"? |
| /** True if the change affected the given item, otherwise false. */ |
| bool changes(key); |
| } |
| |
| /** A change record to a field of an observable object. */ |
| class PropertyChangeRecord extends ChangeRecord { |
| /** The field that was changed. */ |
| final Symbol field; |
| |
| PropertyChangeRecord(this.field); |
| |
| bool changes(key) => key is Symbol && field == key; |
| |
| String toString() => '#<PropertyChangeRecord $field>'; |
| } |
| |
| /** A change record for an observable list. */ |
| class ListChangeRecord extends ChangeRecord { |
| /** The starting index of the change. */ |
| final int index; |
| |
| /** The number of items removed. */ |
| final int removedCount; |
| |
| /** The number of items added. */ |
| final int addedCount; |
| |
| ListChangeRecord(this.index, {this.removedCount: 0, this.addedCount: 0}) { |
| if (addedCount == 0 && removedCount == 0) { |
| throw new ArgumentError('added and removed counts should not both be ' |
| 'zero. Use 1 if this was a single item update.'); |
| } |
| } |
| |
| /** Returns true if the provided index was changed by this operation. */ |
| bool changes(key) { |
| // If key isn't an int, or before the index, then it wasn't changed. |
| if (key is! int || key < index) return false; |
| |
| // If this was a shift operation, anything after index is changed. |
| if (addedCount != removedCount) return true; |
| |
| // Otherwise, anything in the update range was changed. |
| return key < index + addedCount; |
| } |
| |
| String toString() => '#<ListChangeRecord index: $index, ' |
| 'removed: $removedCount, addedCount: $addedCount>'; |
| } |