Question

我有一个核心数据配方对象，其中包含成分对象的有序列表。

成分在UITableView中显示为列表。当用户取消编辑表格视图时，我在MOC上调用rollback，这可能会恢复某些成分（用户已删除的任何成分）并删除其他成分（用户添加的任何内容）。我想为插入/删除设置动画，以便转换不会受到刺激。

这比起初看起来有点困难，特别是因为如果你插入和移除相同的单元格，UITableView会破解毛球。

那里有一些示例代码可以帮助我指导正确的方向吗？现在我使用NSMutableSets进行了一个非常复杂的设置，这种设置不太正常。

NSMutableArray *preIngredients = [NSMutableArray arrayWithArray:[recipe orderedIngredients]];

[self.recipe.managedObjectContext rollback];

NSMutableArray *postIngredients = [NSMutableArray arrayWithArray:[recipe orderedIngredients]];

NSMutableSet *beforeIngredients = [NSMutableSet setWithArray:preIngredients];
NSMutableSet *afterIngredients = [NSMutableSet setWithArray:postIngredients];

NSMutableSet *restoredIngredients = [NSMutableSet setWithSet:afterIngredients];
[restoredIngredients minusSet:beforeIngredients];

NSMutableSet *removedIngredients = [NSMutableSet setWithSet:beforeIngredients];
[removedIngredients minusSet:afterIngredients];

NSMutableSet *allIngredients = [NSMutableSet setWithSet:beforeIngredients];
[allIngredients unionSet:afterIngredients];

int whatToDo[[preIngredients count]];
for (int i = 0; i < [preIngredients count]; i++)
    whatToDo[i] = 0;

for (Ingredient *ingredient in preIngredients) {
    int row = [preIngredients indexOfObject:ingredient];

    if ([removedIngredients containsObject:ingredient])
        whatToDo[row]--;

    if ([restoredIngredients containsObject:ingredient])
        whatToDo[row]++;
}

for (int i = 0; i < [preIngredients count]; i++) {
    if (whatToDo[i] < 0)
        [rowsToRemove addObject:[NSIndexPath indexPathForRow:i inSection:0]];
    else if (whatToDo[i] > 0)
        [rowsToRestore addObject:[NSIndexPath indexPathForRow:i inSection:0]];
}

    // Also remove the "add new ingredient" cell
NSIndexPath *insertNewCellIndexPath = [NSIndexPath indexPathForRow:[preIngredients count] inSection:0];
if ([rowsToRestore indexOfObjectIdenticalTo:insertNewCellIndexPath] == NSNotFound)
    [rowsToRemove addObject:insertNewCellIndexPath];
else
    [rowsToRestore removeObjectIdenticalTo:insertNewCellIndexPath];

[self.tableView insertRowsAtIndexPaths:rowsToRestore withRowAnimation:UITableViewRowAnimationTop];
[self.tableView deleteRowsAtIndexPaths:rowsToRemove withRowAnimation:UITableViewRowAnimationTop];

Answer 1

您是否考虑过使用NSUndoManager？它应该将您的所有更改包装到单个事务中，您可以使用一行代码进行备份。我建议您查看此功能的documentation。

更新

使用NSUndoManager并不复杂。您开始分组，然后结束分组。如果需要，您可以回滚这些更改。与您尝试手动进行的跟踪相比，有几行代码。

Answer 2

这是工作代码，大量使用集合。如果您知道简化它的方法，请不要犹豫：:)

[self.tableView beginUpdates];

NSMutableArray *preIngredients = [NSMutableArray arrayWithArray:[recipe orderedIngredients]];
[self.recipe.managedObjectContext rollback];
NSMutableArray *postIngredients = [NSMutableArray arrayWithArray:[recipe orderedIngredients]];

NSMutableSet *beforeIngredients = [NSMutableSet setWithArray:preIngredients];
NSMutableSet *afterIngredients = [NSMutableSet setWithArray:postIngredients];

NSMutableSet *ingredientsToRestore = [NSMutableSet setWithSet:afterIngredients];
[ingredientsToRestore minusSet:beforeIngredients];

NSMutableSet *ingredientsToRemove = [NSMutableSet setWithSet:beforeIngredients];
[ingredientsToRemove minusSet:afterIngredients];

NSMutableSet *indexPathsToRestore = [NSMutableSet setWithCapacity:[ingredientsToRestore count]];
NSMutableSet *indexPathsToRemove = [NSMutableSet setWithCapacity:[ingredientsToRemove count]];

for (Ingredient *ingredient in ingredientsToRemove)
    [indexPathsToRemove addObject:[NSIndexPath indexPathForRow:[preIngredients indexOfObject:ingredient] inSection:0]];

// Also remove the "add new ingredient" row
[indexPathsToRemove addObject:[NSIndexPath indexPathForRow:[preIngredients count] inSection:0]];

for (Ingredient *ingredient in ingredientsToRestore)
    [indexPathsToRestore addObject:[NSIndexPath indexPathForRow:[postIngredients indexOfObject:ingredient] inSection:0]];

NSMutableSet *commonIndexPaths = [NSMutableSet setWithSet:indexPathsToRemove];
[commonIndexPaths intersectSet:indexPathsToRestore];

[indexPathsToRemove minusSet:commonIndexPaths];
[indexPathsToRestore minusSet:commonIndexPaths];

[self.tableView insertRowsAtIndexPaths:[indexPathsToRestore allObjects] withRowAnimation:UITableViewRowAnimationTop];
[self.tableView deleteRowsAtIndexPaths:[indexPathsToRemove allObjects] withRowAnimation:UITableViewRowAnimationTop];

[self.tableView endUpdates];

在基于Core Data对象的UITableView中插入/删除单元格的算法？

2 个答案:

更新