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基于核心数据对象的UITableView单元格插入/删除算法?

delete-row core-data uitableview

Frank Schmitt · 技术社区 · 15 年前

我有一个核心数据配方对象,它包含一个成分对象的有序列表。

配料在UITableView中显示为列表。当用户取消编辑表视图时,我调用 rollback 在MOC上,它可以恢复一些成分(用户删除的任何成分)并删除其他成分(用户添加的任何成分)。我想动画的插入/删除,以便过渡是不是不和谐。

这比一开始看起来要难一点,特别是当你插入和移除同一个单元格时,UITableView会砍掉一个毛球。

有没有一些示例代码可以帮助我朝着正确的方向发展?现在,我有一个可笑的复杂设置使用NSMutableSets是不是很正常工作。

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];

2 回复 | 直到 15 年前

Marcus S. Zarra 15 年前

你考虑过使用 NSUndoManager documentation 在这个功能上。

更新

使用NSUndoManager一点也不复杂。开始分组,然后结束分组。如果需要,可以回滚这些更改。一对夫妇的代码行相比,跟踪你正在试图做的手。

Frank Schmitt 15 年前

这是大量使用集合的工作代码。如果你知道一个简化的方法,不要犹豫说出来:)

[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];