观察UITextView文本属性的关键值？

Question

我有最糟糕的时间获得关键值观察工作与UITextView的文本属性。我可以成功添加观察者，我甚至可以删除同一个观察者。我有一个tableview与几个单元格 - 一些有UITextFields，一些有UISegmentSelectors和一个有一个UITextView。我的核心数据对象（NSMangedObject的子类）成功观察了其余所有字段，除了UITextView以外。如果需要，我可以发布代码。

发布代码：

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{ 
static NSString *UserProfileCellIdentifier = @"UserProfileCellIdentifier"; 

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier: 
         UserProfileCellIdentifier]; 
if (cell == nil) 
{ 
    [_tableCellsNib instantiateWithOwner:self options:nil]; 

    switch (indexPath.row) 
    { 
      // UserName Row 
     case UserNameRowIndex: 
      _textFieldCell.cellLabel.text = NSLocalizedString(@"UserNameLabel", @"User Profile TableView"); 
      _textFieldCell.cellType = CellTypeNormal; 
      _textFieldCell.boundProperty = @"UserName"; 
      _textFieldCell.tag = indexPath.row; 
      _textFieldCell.errorHandler = self; 
      _textFieldCell.boundControl = _textFieldCell.cellTextField; 

      [_textFieldCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellTextField.text" options:NSKeyValueObservingOptionNew context:NULL]; 

      cell = _textFieldCell; 

      self.textFieldCell = nil; 
      break; 
     case PasswordRowIndex: 
      _textFieldCell.cellLabel.text = NSLocalizedString(@"PasswordLabel", @"User Profile TableView"); 
      _textFieldCell.cellType = CellTypeNormal; 
      _textFieldCell.cellTextField.secureTextEntry = YES; 
      _textFieldCell.boundProperty = @"Password"; 
      _textFieldCell.tag = indexPath.row; 
      _textFieldCell.errorHandler = self; 
      _textFieldCell.boundControl = _textFieldCell.cellTextField; 

      [_textFieldCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellTextField.text" options:NSKeyValueObservingOptionNew context:NULL]; 

      cell = _textFieldCell; 

      self.textFieldCell = nil; 
      break; 
     case PasswordConfirmRowIndex: 
      _textFieldCell.cellLabel.text = NSLocalizedString(@"PasswordConfirmLabel", @"User Profile TableView"); 
      _textFieldCell.cellType = CellTypeNormal; 
      _textFieldCell.cellTextField.secureTextEntry = YES; 
      _textFieldCell.tag = indexPath.row; 

      cell = _textFieldCell; 

      self.textFieldCell = nil; 
      break; 
     case FirstNameRowIndex: 
      _textFieldCell.cellLabel.text = NSLocalizedString(@"FirstNameLabel", @"User Profile TableView"); 
      _textFieldCell.cellType = CellTypeNormal; 
      _textFieldCell.boundProperty = @"FirstName"; 
      _textFieldCell.tag = indexPath.row; 
      _textFieldCell.errorHandler = self; 
      _textFieldCell.boundControl = _textFieldCell.cellTextField; 

      [_textFieldCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellTextField.text" options:NSKeyValueObservingOptionNew context:NULL]; 
      cell = _textFieldCell; 

      self.textFieldCell = nil; 
      break; 
     case LastNameRowIndex: 
      _textFieldCell.cellLabel.text = NSLocalizedString(@"LastNameLabel", @"User Profile TableView"); 
      _textFieldCell.cellType = CellTypeNormal; 
      _textFieldCell.boundProperty = @"LastName"; 
      _textFieldCell.tag = indexPath.row; 
      _textFieldCell.errorHandler = self; 
      _textFieldCell.boundControl = _textFieldCell.cellTextField; 

      [_textFieldCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellTextField.text" options:NSKeyValueObservingOptionNew context:NULL]; 
      cell = _textFieldCell; 

      self.textFieldCell = nil; 
      break; 
     case DateOfBirthRowIndex: 
      _textFieldCell.cellLabel.text = NSLocalizedString(@"BirthDateLabel", @"User Profile TableView"); 
      _textFieldCell.cellType = CellTypeDatePicker; 
      _textFieldCell.boundProperty = @"DateOfBirth"; 
      _textFieldCell.tag = indexPath.row; 
      _textFieldCell.errorHandler = self; 
      _textFieldCell.boundControl = _textFieldCell.cellTextField; 

      [_textFieldCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellTextField.text" options:NSKeyValueObservingOptionNew context:NULL]; 
      cell = _textFieldCell; 

      self.textFieldCell = nil; 
      break; 
     case GenderSelfRowIndex: 
      _genderSelectCell.cellLabel.text = NSLocalizedString(@"UserSexLabel", @"User Profile TableView"); 
      _genderSelectCell.boundProperty = @"GenderSelf"; 
      _genderSelectCell.errorHandler = self; 
      _genderSelectCell.boundControl = _genderSelectCell.cellGenderSegment; 
      _genderSelectCell.tag = indexPath.row; 

      [_genderSelectCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellGenderSegment.selectedSegmentIndex" options:NSKeyValueObservingOptionNew context:NULL]; 
      cell = _genderSelectCell; 

      self.genderSelectCell = nil; 
      break; 
     case GenderInterestedInRowIndex: 
      _genderSelectCell.cellLabel.text = NSLocalizedString(@"UserInterestedInLabel", @"User Profile TableView"); 
      _genderSelectCell.boundProperty = @"GenderInterestedIn"; 
      _genderSelectCell.errorHandler = self; 
      _genderSelectCell.boundControl = _genderSelectCell.cellGenderSegment; 
      _genderSelectCell.tag = indexPath.row; 

      [_genderSelectCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellGenderSegment.selectedSegmentIndex" options:NSKeyValueObservingOptionNew context:NULL]; 
      cell = _genderSelectCell; 

      self.genderSelectCell = nil; 
      break; 
     case IntroductionRowIndex: 
      _textViewCell.cellLabel.text = NSLocalizedString(@"IntroductionLabel", @"User Profile TableView"); 
      _textViewCell.boundControl = _textViewCell.cellTextView; 
      _textViewCell.errorHandler = self; 
      _textViewCell.boundProperty = @"Introduction"; 
      _textViewCell.tag = indexPath.row; 

      [_textViewCell addObserver:[MBUtilities getAppDelegate].userProfile forKeyPath:@"cellTextView.text" options:NSKeyValueObservingOptionNew context:NULL]; 
      cell = _textViewCell; 

      self.textViewCell = nil; 
      break; 
    }; 
} 

return cell; 
} 

讨论：每个小区从外部NIB文件，然后用不同的属性进行初始化加载。除了UITextView的最后一个外，所有单元格都可以使用键值观察。让我知道是否需要任何额外的信息。

Answer 1

UIKit的是不能保证KVO compliant：

注：虽然UIKit框架中的类一般不支持志愿，你仍然可以实现它在你的应用程序的自定义对象，包括自定义观点。

它可能适用于某些类+键，但这不可靠，并可能在不同的iOS版本中更改。见Dave’s answer to this question; Dave在UIKit上工作。

Answer 2

您是否尝试过实现UITextViewDelegate并将thisIsYourTextView.delegate赋值给它？

嗯，我发现这tutorial，也许它会让事情更清楚一点。

Answer 3

好的，所以我没有找到任何解释此行为的运气，除非有人能告诉我，否则我相信它是IOS中的一个错误。

我能得到它与这个技巧的工作：

- (void)textViewDidEndEditing:(UITextView *)textView 
{ 
    NSLog(@"Editing Ended"); 
    textView.text = textView.text; 
} 

一旦加入该代码，瞧，在observeValueForKeyPath火灾！

Answer 4

使用UITextViewTextDidChangeNotification更好。

我做了以下内容：与NSNotificationCenter

第一寄存器：

- (id)init 
{ 
    [super init]; 
    if (self) 
    { 
     NSNotificationCenter *nc = [NSNotificationCenter defaultCenter]; 
     [nc addObserver:self 
       selector:@selector(textDidChange:) 
        name:UITextViewTextDidChangeNotification 
       object:nil]; 
    } 
    return self; 
} 

- (void)dealloc 
{ 
    NSNotificationCenter *nc = [NSNotificationCenter defaultCenter]; 
    [nc removeObserver:self]; 
} 

然后定义一个通知处理程序：

- (void)textDidChange:(NSNotification *)note 
{ 
    NSLog(@"Observation..."); 
} 

现在，每当文本的UITextView的对象的变化，textDidChange:方法将被调用。