blocks|key|1410208|text|fetchRequest是一个只读属性。您的帖子中的代码行将不起作用。如果你想使用不同的fetch请求，你需要用一个新的NSFetchedResultsController替换你的控制器。您的表不会自动重新加载。在更换了NSFetchedResultsController之后，您需要向它发送一条reloadData消息。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1410209|entityMap^0|0|C|1O|Q|32|Q|44|A|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|G|$]]

<code>fetchRequest</code> is a read-only property. The line of code in your post will not work. If you want to use a different fetch request, you'll need to replace your controller with a new <code>NSFetchedResultsController</code>. Your table won't reload automatically. You'll need to send it a <code>reloadData</code> message some time after you've replaced the <code>NSFetchedResultsController</code>.

blocks|key|1194930|text|不使用NSFetchedResultsController作为表视图数据源，而是创建一个NSArray，当用户根据获取的结果使用分段控件更改排序顺序时，可以设置该your。然后使用标准数组排序进行排序。如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1194931|-+(IBAction)segmentChanged:(id)sender
{
++++//+Determine+which+segment+is+selected+and+then+set+this+
++++//+variable+accordingly
++++BOOL+ascending+=+([sender+selectedSegmentIndex]+==+0);

++++NSArray+*allObjects+=+[fetchedResultsController+fetchedObjects];

++++NSSortDescriptor+*sortNameDescriptor+=+
+++++++++++++++++++++++[[[NSSortDescriptor+alloc]+initWithKey:@"name"+
+++++++++++++++++++++++++++++++++ascending:ascending]+autorelease];

++++NSArray+*sortDescriptors+=+[[[NSArray+alloc]+
+++++++++++++++++++++initWithObjects:sortNameDescriptor,+nil]+autorelease];

++++//+items+is+a+synthesized+ivar+that+we+use+as+the+table+view
++++//+data+source.
++++[self+setItems:[allObjects+sortedArrayUsingDescriptors:sortDescriptors]];

++++//+Tell+the+tableview+to+reload.
++++[itemsTableView+reloadData];++++
}|code-block|syntax|javascript|1194932|因此，我使用的排序描述符名为"+name+"，但您需要将其更改为您希望在获取的结果中排序的字段的名称。另外，我引用的ivar项将成为新的表视图数据源。您的表视图委托现在将如下所示：|1194933|-+(NSInteger)tableView:(UITableView*)tableView+
+numberOfRowsInSection:(NSInteger)section
{
++++return+[items+count];
}

-+(UITableViewCell+*)tableView:(UITableView+*)tableView
+++++++++cellForRowAtIndexPath:(NSIndexPath+*)indexPath
{
++++//+Get+your+table+cell+by+reuse+identifier+as+usual+and+then+grab+one+of
++++//+your+records+based+on+the+index+path
++++//+...

++++MyManagedObject+*object+=+[items+objectAtIndex:[indexPath+row]];

++++//+Set+your+cell+label+text+or+whatever+you+want+
++++//+with+one+of+the+managed+object's+fields.
++++//+...

++++return+cell;
}|1194934|我不确定这是不是最好的方法，但它应该是可行的。|1194935|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Instead of using your NSFetchedResultsController as your table view data source, create an NSArray that you set when the user changes sort order with your segmented control basing the array contents on the fetched results. Then just sort using standard array sorting. Something like this:

<pre><code>- (IBAction)segmentChanged:(id)sender
{
 // Determine which segment is selected and then set this 
 // variable accordingly
 BOOL ascending = ([sender selectedSegmentIndex] == 0);

 NSArray *allObjects = [fetchedResultsController fetchedObjects];

 NSSortDescriptor *sortNameDescriptor = 
 [[[NSSortDescriptor alloc] initWithKey:@"name" 
 ascending:ascending] autorelease];

 NSArray *sortDescriptors = [[[NSArray alloc] 
 initWithObjects:sortNameDescriptor, nil] autorelease];

 // items is a synthesized ivar that we use as the table view
 // data source.
 [self setItems:[allObjects sortedArrayUsingDescriptors:sortDescriptors]];

 // Tell the tableview to reload.
 [itemsTableView reloadData]; 
}
</code></pre>

So the sort descriptor I've used is called "name", but you would change this to the name of the field you want to sort by in the fetched results. Also, the items ivar I've referenced would be your new table view data source. Your table view delegates would now be something like this:

<pre><code>- (NSInteger)tableView:(UITableView*)tableView 
 numberOfRowsInSection:(NSInteger)section
{
 return [items count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView
 cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
 // Get your table cell by reuse identifier as usual and then grab one of
 // your records based on the index path
 // ...

 MyManagedObject *object = [items objectAtIndex:[indexPath row]];

 // Set your cell label text or whatever you want 
 // with one of the managed object's fields.
 // ...

 return cell;
}
</code></pre>

Not sure if this is the best way, but it should work.

blocks|key|1410389|text|我遇到了同样的问题，只需在FetchRequestController的FetchRequest上设置排序描述符，然后执行fetch+(performFetch)，最后在表视图上重新加载数据，就可以解决这个问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1410390|NSArray+*sortDescriptors+=+[NSArray+arrayWithObject:+sorter];
[[fetchedResultsController+fetchRequest]+setSortDescriptors:sortDescriptors];
NSError+*error;
if+(![[self+fetchedResultsController]+performFetch:&error])+{
++++++++//+Handle+you+error+here
}
[sorter+release];
[myTableView+reloadData];|code-block|syntax|javascript|1410391|对于我来说，这是最简单的方式来处理变化，在飞行中排序，而不会丢失FRC或做任何其他花哨的对象处理。我不确定这对性能的影响，如果表中的行集很大，可能会产生影响。|1410392|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I was stuck with the same problem and I could fix it with just setting the sort descriptors on the FetchRequestController's FetchRequest, then execute a fetch (performFetch) and finally reload the data on the table view.

<pre><code>NSArray *sortDescriptors = [NSArray arrayWithObject: sorter];
[[fetchedResultsController fetchRequest] setSortDescriptors:sortDescriptors];
NSError *error;
if (![[self fetchedResultsController] performFetch:&amp;error]) {
 // Handle you error here
}
[sorter release];
[myTableView reloadData];
</code></pre>

This was the easiest way for me to deal with the change the sorting on the fly without dropping the FRC or do any other fancy object handling. I am not sure about the performance implications on that and it could have an impact if the set of rows in the table is huge.

blocks|key|1410464|text|Andreas+Schaefer的回答对我很有效。诀窍是为fetch请求设置一个新参数，以及它是否是下面的代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1410465|[[fetchedResultsController+fetchRequest]+setSortDescriptors:sortDescriptors];|code-block|syntax|javascript|1410466|或|1410467|[[fetchedResultsController+fetchRequest]+setPredicate:predicate];|1410468|在调用此函数之前：|1410469|if+(![[self+fetchedResultsController]+performFetch:&error])+{
++++++++//+Handle+you+error+here
}

[self.tableView+reloadData];|1410470|似乎当您设置新参数时，NSFetchedResultsController将根据您设置的内容执行新的fetchrequest。如果不设置新的参数，它就不会执行重新获取，只调用performFetch就不会工作。|offset|length|style|CODE|1410471|希望这能帮助其他人..|1410472|entityMap^0|0|0|0|0|0|0|2F|C|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|10|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|12|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|14|8|@$Q|15|R|16|S|T]]|9|@]|A|$]]|$1|U|3|V|5|6|7|17|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|18|8|@]|9|@]|A|$]]]|X|$]]

Andreas Schaefer answer worked for me. The trick is setting a new parameter for the fetch request with whether it is this code: 

<pre><code>[[fetchedResultsController fetchRequest] setSortDescriptors:sortDescriptors];
</code></pre>

OR

<pre><code>[[fetchedResultsController fetchRequest] setPredicate:predicate];
</code></pre>

Before calling this:

<pre><code>if (![[self fetchedResultsController] performFetch:&amp;error]) {
 // Handle you error here
}

[self.tableView reloadData];
</code></pre>

it appears that when you set a new parameter, than the NSFetchedResultsController will perform a new fetchrequest based upon what you set.. Without setting a new parameter, it won't perform the re-fetch and just calling <code>performFetch</code> it won't work..

Hope this helps someone else..

I'm trying to change the sorting in a NSFetchController on the fly, by some sort of segmented control. To either sort A->Z Z->A type thing.

What do I have to do to do this? I'm following Jeff Lamarche's example here: <a href="http://iphonedevelopment.blogspot.com/2009/11/navigation-based-application-core-data.html" rel="noreferrer" title="here">Here</a> 

Do I need to make a new NSFetchedResultsController and then set it, or do I just make a new NSFetchRequest and do

<pre><code>fetchedResultController.fetchRequest = newFetchRequest
</code></pre>

and then my table will automatically update?

Changing the Sorting in an NSFetchedResultsController on the fly

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在尝试通过某种分段控制来动态地更改NSFetchController中的排序。排序A->Z Z->A类型的东西。我要怎么做才能做到这一点？我在这里遵循Jeff Lamarche的例子：我是需要创建一个新的NSFetchedResultsController然后对其进行设置，还是只创建一个新的NSFetchReque...

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