Index: packages/collection/lib/src/union_set_controller.dart |
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+// 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. |
+ |
+import 'union_set.dart'; |
+ |
+/// A controller that exposes a view of the union of a collection of sets. |
+/// |
+/// This is a convenience class for creating a [UnionSet] whose contents change |
+/// over the lifetime of a class. For example: |
+/// |
+/// ```dart |
+/// class Engine { |
+/// Set<Test> get activeTests => _activeTestsGroup.set; |
+/// final _activeTestsGroup = new UnionSetController<Test>(); |
+/// |
+/// void addSuite(Suite suite) { |
+/// _activeTestsGroup.add(suite.tests); |
+/// _runSuite(suite); |
+/// _activeTestsGroup.remove(suite.tests); |
+/// } |
+/// } |
+/// ``` |
+class UnionSetController<E> { |
+ /// The [UnionSet] that provides a view of the union of sets in [this]. |
+ UnionSet<E> get set => _set; |
+ UnionSet<E> _set; |
+ |
+ /// The sets whose union is exposed through [set]. |
+ final _sets = new Set<Set<E>>(); |
+ |
+ /// Creates a set of sets that provides a view of the union of those sets. |
+ /// |
+ /// If [disjoint] is `true`, this assumes that all component sets are |
+ /// disjoint—that is, that they contain no elements in common. This makes |
+ /// many operations including [length] more efficient. |
+ UnionSetController({bool disjoint: false}) { |
+ _set = new UnionSet<E>(_sets, disjoint: disjoint); |
+ } |
+ |
+ /// Adds the contents of [component] to [set]. |
+ /// |
+ /// If the contents of [component] change over time, [set] will change |
+ /// accordingly. |
+ void add(Set<E> component) { |
+ _sets.add(component); |
+ } |
+ |
+ /// Removes the contents of [component] to [set]. |
+ /// |
+ /// If another set in [this] has overlapping elements with [component], those |
+ /// elements will remain in [set]. |
+ bool remove(Set<E> component) => _sets.remove(component); |
+} |