pkg/mdv_observe/lib/src/observable_box.dart

// 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 mdv_observe;

// TODO(jmesserly): should the property name be configurable?
// That would be more convenient.
/**
 * An observable box that holds a value. Use this if you want to store a single
 * value. For other cases, it is better to use [ObservableList],
 * [ObservableMap], or a custom [Observable] implementation based on
 * [ObservableMixin]. The property name for changes is "value".
 */
class ObservableBox<T> extends ObservableBase {
  static const _VALUE = const Symbol('value');

  T _value;

  ObservableBox([T initialValue]) : _value = initialValue;

  T get value => _value;

  void set value(T newValue) {
    _value = notifyPropertyChange(_VALUE, _value, newValue);
  }

  String toString() => '#<$runtimeType value: $value>';

  getValueWorkaround(key) {
    if (key == _VALUE) return value;
    return null;
  }
  void setValueWorkaround(key, newValue) {
    if (key == _VALUE) value = newValue;
  }
}