// 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.

library observe.src.bind_property;

import 'dart:async';
import 'package:observe/observe.dart';

/// Forwards an observable property from one object to another. For example:
///
///     class MyModel extends Observable {
///       StreamSubscription _sub;
///       MyOtherModel _otherModel;
///
///       MyModel() {
///         ...
///         _sub = onPropertyChange(_otherModel, #value,
///             () => notifyProperty(this, #prop);
///       }
///
///       String get prop => _otherModel.value;
///       set prop(String value) { _otherModel.value = value; }
///     }
///
/// See also [notifyProperty].
// TODO(jmesserly): make this an instance method?
StreamSubscription onPropertyChange(Observable source, Symbol sourceName,
    void callback()) {
  return source.changes.listen((records) {
    for (var record in records) {
      if (record is PropertyChangeRecord &&
          (record as PropertyChangeRecord).name == sourceName) {
        callback();
        break;
      }
    }
  });
}