pragma mark - 重新订购

Question

我正在尝试在iOS应用程序中重新排序UITableView 在收获了很多StackOverFlow问题后，我使用了这个：

- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath {
    self.userDrivenDataModelChange = YES;

    NSUInteger fromIndex = fromIndexPath.row;  
    NSUInteger toIndex = toIndexPath.row;

    NSManagedObject *affectedObject = [self.fetchedResultsController.fetchedObjects objectAtIndex:fromIndex];  
    [affectedObject setValue: [NSNumber numberWithInt:toIndex] forKey:@"priority"];

    NSUInteger start, end;
    int delta;

    if (fromIndex < toIndex) {
        // move was down, need to shift up
        delta = -1;
        start = fromIndex + 1;
        end = toIndex;
    } else { // fromIndex > toIndex
        // move was up, need to shift down
        delta = 1;
        start = toIndex;
        end = fromIndex - 1;
    }

    for (NSUInteger i = start; i <= end; i++) {
        NSManagedObject *otherObject = [self.fetchedResultsController.fetchedObjects objectAtIndex:i];  
        NSNumber *oldPriority = (NSNumber *)[otherObject valueForKey:@"priority"];
        int tmp = [oldPriority intValue] + delta;
        NSNumber *newPriority = [NSNumber numberWithInt:tmp];
        [otherObject setValue: [NSNumber numberWithInt:[newPriority intValue]] forKey:@"priority"];        
    }


    NSError *error = nil;
    if (! [self.fetchedResultsController.managedObjectContext save:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    // Should I call something here?

    self.userDrivenDataModelChange = NO;
}

将保存消息发送到上下文对象后，我该怎么办？获取控制器或表视图上的某些方法？因为它不能以当前的形状工作。

我应该首先将保存发送到上下文对象吗？

Answer 1

您已经向managedObjectContext发送了保存消息，这很好，if (! [self.fetchedResultsController.managedObjectContext save:&error])。

要在表格视图中查看更新的结果，在此方法结束时调用[tableView reloadData];可能就足够了。

Answer 2

您还应该检查索引路径是否相等，如果它们都崩溃了！

if([toIndexPath isEqual:fromIndexPath]) return;

Answer 3

//上面的答案是正确的。我的自己的对象名称将是另一个正常工作的例子

pragma mark - 重新订购

（BOOL）tableView：（UITableView *）tableView canMoveRowAtIndexPath：（NSIndexPath *）indexPath { return indexPath.section == 0＆amp;＆amp; indexPath.row＆lt; self.list.sortedTasks.count; }
（void）tableView：（UITableView *）tableView moveRowAtIndexPath：（NSIndexPath *）sourceIndexPath toIndexPath：（NSIndexPath *）destinationIndexPath {

NSInteger fromIndex = sourceIndexPath.row; NSInteger toIndex = destinationIndexPath.row;

Task * movingTask = [self.list.sortedTasks objectAtIndex：sourceIndexPath.row]; Task * destinationTask = [self.list.sortedTasks objectAtIndex：destinationIndexPath.row];

NSArray * tempList = self.list.sortedTasks;

if（fromIndex == toIndex）{     返回; }

//将活动任务移动到目标任务的位置。 movingTask.order = destinationTask.order; NSLog（@＆＃34;将％@移动到％@＆＃34;，movingTask.details，movingTask.order）;

NSUInteger开始，结束; int order;

if（fromIndex＆lt; toIndex）{     //移动了，需要向上移动     order = -1;     start = fromIndex + 1;     end = toIndex; } else {// fromIndex＆gt; toIndex     //移动了，需要向下移动     order = 1;     start = toIndex;     end = fromIndex - 1; }

for（     NSUInteger i =开始;我＆lt; =结束;我++）{     Task * otherObject = [tempList objectAtIndex：i];     NSNumber * oldPriority = otherObject.order;     int tmp = [oldPriority intValue] + order;     NSNumber * newPriority = [NSNumber numberWithInt：tmp];     otherObject.order = newPriority;
```
NSLog(@"moving %@ to %@", otherObject.details, otherObject.order);
```
}

[self.managedObjectContext save：nil];

}

最后一篇解决重新排序的UITableView支持Core Data难题

3 个答案:

pragma mark - 重新订购