Dart DocumentationobserveListChangeRecord

ListChangeRecord class

A change record for an observable list.

class ListChangeRecord extends ChangeRecord {
 /** The starting index of the change. */
 final int index;

 /** The number of items removed. */
 final int removedCount;

 /** The number of items added. */
 final int addedCount;

 ListChangeRecord(this.index, {this.removedCount: 0, this.addedCount: 0}) {
   if (addedCount == 0 && removedCount == 0) {
     throw new ArgumentError('added and removed counts should not both be '
         'zero. Use 1 if this was a single item update.');
   }
 }

 /** Returns true if the provided index was changed by this operation. */
 bool changes(key) {
   // If key isn't an int, or before the index, then it wasn't changed.
   if (key is! int || key < index) return false;

   // If this was a shift operation, anything after index is changed.
   if (addedCount != removedCount) return true;

   // Otherwise, anything in the update range was changed.
   return key < index + addedCount;
 }

 String toString() => '#<ListChangeRecord index: $index, '
     'removed: $removedCount, addedCount: $addedCount>';
}

Extends

ChangeRecord > ListChangeRecord

Constructors

new ListChangeRecord(int index, {int removedCount: 0, int addedCount: 0}) #

ListChangeRecord(this.index, {this.removedCount: 0, this.addedCount: 0}) {
 if (addedCount == 0 && removedCount == 0) {
   throw new ArgumentError('added and removed counts should not both be '
       'zero. Use 1 if this was a single item update.');
 }
}

Properties

final int addedCount #

The number of items added.

final int addedCount

final int index #

The starting index of the change.

final int index

final int removedCount #

The number of items removed.

final int removedCount

Methods

abstract bool change(key) #

inherited from ChangeRecord

True if the change affected the given item, otherwise false.

bool changes(key) #

Returns true if the provided index was changed by this operation.

bool changes(key) {
 // If key isn't an int, or before the index, then it wasn't changed.
 if (key is! int || key < index) return false;

 // If this was a shift operation, anything after index is changed.
 if (addedCount != removedCount) return true;

 // Otherwise, anything in the update range was changed.
 return key < index + addedCount;
}

String toString() #

Returns a string representation of this object.

docs inherited from Object
String toString() => '#<ListChangeRecord index: $index, '
   'removed: $removedCount, addedCount: $addedCount>';