Implement Model-Driven-Views spec for Dart

pkg/observe/lib/src/observable_list.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 observe;
+
+/**
+ * Represents an observable list of model values. If any items are added,
+ * removed, or replaced, then observers that are listening to [changes]
+ * will be notified.
+ */
+// TODO(jmesserly): remove implements List<E> once we can extend ListBase<E>
+class ObservableList<E> extends _ListBaseWorkaround with ObservableMixin
+    implements List<E> {
+
+  static const _LENGTH = const Symbol('length');
+
+  /** The inner [List<E>] with the actual storage. */
+  final List<E> _list;
+
+  /**
+   * Creates an observable list of the given [length].
+   *
+   * If no [length] argument is supplied an extendable list of
+   * length 0 is created.
+   *
+   * If a [length] argument is supplied, a fixed size list of that
+   * length is created.
+   */
+  ObservableList([int length])
+      : _list = length != null ? new List<E>(length) : <E>[];
+
+  /**
+   * Creates an observable list with the elements of [other]. The order in
+   * the list will be the order provided by the iterator of [other].
+   */
+  factory ObservableList.from(Iterable<E> other) =>
+      new ObservableList<E>()..addAll(other);
+
+  // TODO(jmesserly): remove once we have mirrors
+  getValueWorkaround(key) => identical(key, _LENGTH) ? length : null;
+
+  setValueWorkaround(key, value) {
+    if (identical(key, _LENGTH)) length = value;
+  }
+
+  int get length => _list.length;
+
+  set length(int value) {
+    int len = _list.length;
+    if (len == value) return;
+
+    // Produce notifications if needed
+    if (hasObservers) {
+      if (value < len) {
+        // Remove items, then adjust length. Note the reverse order.
+        notifyChange(new ListChangeRecord(value, removedCount: len - value));
+        notifyField(_LENGTH, len, value);
+      } else {
+        // Adjust length then add items
+        notifyField(_LENGTH, len, value);
+        notifyChange(new ListChangeRecord(len, addedCount: value - len));
+      }
+    }
+
+    _list.length = value;
+  }
+
+  E operator [](int index) => _list[index];
+
+  void operator []=(int index, E value) {
+    var oldValue = _list[index];
+    if (hasObservers) {
+      notifyChange(new ListChangeRecord(index, addedCount: 1, removedCount: 1));
+    }
+    _list[index] = value;
+  }
+
+  // The following methods are here so that we can provide nice change events.
+
+  void setAll(int index, Iterable<E> iterable) {
+    if (iterable is! List && iterable is! Set) {
+      iterable = iterable.toList();
+    }
+    var len = iterable.length;
+    _list.setAll(index, iterable);
+    if (hasObservers) {
+      notifyChange(
+          new ListChangeRecord(index, addedCount: len, removedCount: len));
+    }
+  }
+
+  void add(E value) {
+    int len = _list.length;
+    if (hasObservers) {
+      notifyField(_LENGTH, len, len + 1);
+      notifyChange(new ListChangeRecord(len, addedCount: 1));
+    }
+
+    _list.add(value);
+  }
+
+  void addAll(Iterable<E> iterable) {
+    int len = _list.length;
+    _list.addAll(iterable);
+    noitifyChange(new ListChangeRecord(len, addedCount: _list.length - len));
+    notifyField(_LENGTH, len, _list.length);
+  }
+
+  bool remove(Object element) {
+    for (int i = 0; i < this.length; i++) {
+      if (this[i] == element) {
+        removeRange(i, 1);
+        return true;
+      }
+    }
+    return false;
+  }
+
+  void removeRange(int start, int end) {
+    _rangeCheck(start, end);
+    int length = end - start;
+    _list.setRange(start, this.length - length, this, end);
+
+    int len = _list.length;
+    _list.length -= length;
+    if (hasObservers) {
+      notifyChange(new ListChangeRecord(len, removedCount: length));
+      notifyField(_LENGTH, len, _list.length);
+    }
+  }
+
+  void insertAll(int index, Iterable<E> iterable) {

[floitsch, 2013/05/07 14:46:48]

Why is this not just:
var oldLength = _list.length;
_list.insertAll(index, iterable);
var insertionLength = _list.length - OldLength;
...

Replicating the behavior of ListBase seems wrong.

Same for all the other methods.

+    if (index < 0 || index > length) {
+      throw new RangeError.range(index, 0, length);
+    }
+    // TODO(floitsch): we can probably detect more cases.
+    if (iterable is! List && iterable is! Set) {
+      iterable = iterable.toList();
+    }
+    int insertionLength = iterable.length;
+    // There might be errors after the length change, in which case the list
+    // will end up being modified but the operation not complete. Unless we
+    // always go through a "toList" we can't really avoid that.
+    int len = _list.length;
+    _list.length += insertionLength;
+
+    _list.setRange(index + insertionLength, this.length, this, index);
+
+    if (hasObservers) {
+      notifyField(_LENGTH, len, _list.length);
+      notifyChange(new ListChangeRecord(index, addedCount: insertionLength);
+    } else {
+      setAll(index, iterable);
+    }
+  }
+
+  void insert(int index, E element) {
+    if (index < 0 || index > length) {
+      throw new RangeError.range(index, 0, length);
+    }
+    if (index == this.length) {
+      add(element);
+      return;
+    }
+    // We are modifying the length just below the is-check. Without the check
+    // Array.copy could throw an exception, leaving the list in a bad state
+    // (with a length that has been increased, but without a new element).
+    if (index is! int) throw new ArgumentError(index);
+    this.length++;
+    _list.setRange(index + 1, this.length, this, index);
+    notifyChange(new ListChangeRecord(index, addedCount: 1);
+    _list[index] = element;
+  }
+
+
+  E removeAt(int index) {
+    E result = this[index];
+    removeRange(index, index + 1);
+    return result;
+  }
+
+  void _rangeCheck(int start, int end) {
+    if (start < 0 || start > this.length) {
+      throw new RangeError.range(start, 0, this.length);
+    }
+    if (end < start || end > this.length) {
+      throw new RangeError.range(end, start, this.length);
+    }
+  }
+}
+
+
+// TODO(jmesserly): bogus type to workaround spurious VM bug with generic base
+// class and mixins.
+abstract class _ListBaseWorkaround extends ListBase<dynamic> {}