UnionSetController<E> class

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:

class Engine {
  Set<Test> get activeTests => _activeTestsGroup.set;
  final _activeTestsGroup = UnionSetController<Test>();

  void addSuite(Suite suite) {
    _activeTestsGroup.add(suite.tests);
    _runSuite(suite);
    _activeTestsGroup.remove(suite.tests);
  }
}