NSSortDescriptor未被调用

Question

我正在尝试对实体文件夹执行一个fetch请求，并且希望一个名为xyz的文件夹在排序时成为最后一个对象。

  NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription 
                                   entityForName:@"Folder" inManagedObjectContext:appDelegate.managedObjectContext];

    [fetchRequest setEntity:entity];

    NSSortDescriptor *lastDescriptor =
    [[[NSSortDescriptor alloc] initWithKey:@"folderName" ascending:YES comparator:^NSComparisonResult(NSString* name1, NSString* name2) {
        NSLog(@"descriptor");
        if ([name1 isEqualToString:@"xyz"]) {
            return NSOrderedAscending;
        }
        if ([name2 isEqualToString:@"xyz"]) {
            return NSOrderedDescending;
        }

        return [name1 compare:name2];
    }] autorelease];  


    [fetchRequest setSortDescriptors:[NSArray arrayWithObject:lastDescriptor]];
    [fetchRequest setFetchBatchSize:5];

    NSFetchedResultsController *theFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:appDelegate.managedObjectContext sectionNameKeyPath:nil cacheName:nil];
    self.fetchedResultsController = theFetchedResultsController;
    self.fetchedResultsController.delegate=self;   

    [fetchRequest release];
    [theFetchedResultsController release];

    NSError *error;
    if (![[self fetchedResultsController] performFetch:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        exit(-1);  // Fail
    }

但是没有一个NSLog语句被调用。他们应该这么做吗？文件夹xyz不显示在最后，但一切都按字母顺序排序。我做错了什么吗？

编辑：发布了完整的代码

Answer 1

此代码(您的代码)工作：

- (void)sortMe {

    NSDictionary *d0 = [NSDictionary dictionaryWithObject:@"efg" forKey:@"folderName"];
    NSDictionary *d1 = [NSDictionary dictionaryWithObject:@"xyz" forKey:@"folderName"];
    NSDictionary *d2 = [NSDictionary dictionaryWithObject:@"abc" forKey:@"folderName"];
    NSDictionary *d3 = [NSDictionary dictionaryWithObject:@"def" forKey:@"folderName"];
    NSArray *testMe = [NSArray arrayWithObjects:d0, d1, d2, d3, nil];

    NSSortDescriptor *lastDescriptor =
    [[NSSortDescriptor alloc] initWithKey:@"folderName" ascending:YES comparator:^NSComparisonResult(NSString* name1, NSString* name2) {
        NSLog(@"descriptor");
        if ([name1 isEqualToString:@"xyz"]) {
            return NSOrderedAscending;
        }
        if ([name2 isEqualToString:@"xyz"]) {
            return NSOrderedDescending;
        }

        return [name1 compare:name2];
    }];

    NSArray *sorted = [testMe sortedArrayUsingDescriptors:[NSArray arrayWithObject:lastDescriptor]];
    for (NSDictionary *d in sorted) {
        NSLog(@"value=%@", [d valueForKey:@"folderName"]);
    }
}

我预测这段代码也会起作用：

NSError *error;
NSArray *result =  [appDelegate.managedObjectContext executeFetchRequest:fetchRequest error:&error];
// log the array

我认为问题在于代码中其他地方的NSFetchedResultsController委托设置。