(NSManagedObjectContext *)managedObjectContext、NSInvalidArgumentException

Question

我有一个应用程序，可以显示保存在核心数据中的文本。在这个文本中，我添加了一个SearchBar和SearchDisplayController。当我在SearchBar中提示并键入某些内容时，我会立即看到以下内容

NSInvalidArgumentException: **'NSInvalidArgumentException', reason: '-[NSManagedObject compare:options:range:]: unrecognized selector sent to instance 0x8cb6460'**.

0x8cb6460是一个名为tempSearchStr的NSString变量。下面是两段代码：

第一块

- (NSManagedObjectContext *)managedObjectContext
{
    NSManagedObjectContext *context = nil;
    id delegate = [[UIApplication sharedApplication] delegate];
    if ([delegate performSelector:@selector(managedObjectContext)]) {
        context = [delegate managedObjectContext];
    }

    return context;
}

第二个区块

- (void)searchInNoteMe
{
    NSString *searchString = self.searchBar.text;

    for (NSString *tempSearchStr in notemearray) {
        NSComparisonResult NSCResult = [tempSearchStr compare:searchString
                                                      options:(NSCaseInsensitiveSearch|NSDiacriticInsensitiveSearch)
                                                        range:NSMakeRange(0, [searchString length])];
        if (NSCResult == NSOrderedSame) {
            [notemearrayfiltered addObject:tempSearchStr];
        }
    }
}

notemearray的代码

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    NSManagedObjectContext *moc = [self managedObjectContext];
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:@"NoteMe"];
    notemearray = [[moc executeFetchRequest:fetchRequest
                                      error:nil] mutableCopy];

    notemearrayfiltered = [[NSMutableArray alloc] initWithArray:notemearray];
    [self.tableView reloadData];
}

Answer 1

notemearray包含NSManagedObject%s而不是NSString%s，这是异常告诉您的。

您希望在CoreData对象的noteme属性上调用compare:options:range:。

- (void)searchInNoteMe
{
    NSString *searchString = self.searchBar.text;

    for (NSManagedObject *note in notemearray) {
        NSString *noteString = [note valueForKey:@"noteme"];
        NSComparisonResult NSCResult = [noteString compare:searchString 
                                                   options:(NSCaseInsensitiveSearch|NSDiacriticInsensitiveSearch)
                                                     range:NSMakeRange(0, [searchString length])];
        if (NSCResult == NSOrderedSame) {
            [notemearrayfiltered addObject:note];
        }
    }
}

如果要更新NSManagedObject上的noteme属性，可以执行以下操作：

[note setValue:@"New string" forKey:@"noteme"];