Question

I’m having the worst time getting key value observing working in with a UITextView’s text property. I can successfully add the observer, I can even remove that same observer. I have a tableview with several cells – some have UITextFields, some have UISegmentSelectors and one has a UITextView. ALL the rest of the fields are successfully observed by my core data object (subclass of NSMangedObject) EXCEPT for the UITextView. I can post code if needed.

Posted Code:

- (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;
}

Discussion: Each cell is loaded from an external NIB file then initialized with different properties. All of the cells work with key value observing except for the very last one with the UITextView. Let me know if any additional info is needed.

Answer 1

UIKit is not guaranteed to be KVO compliant:

Note: Although the classes of the UIKit framework generally do not support KVO, you can still implement it in the custom objects of your application, including custom views.

It might work on some classes + keys but that’s not reliable, and might change across different iOS versions. See Dave’s answer to this question; Dave works on UIKit.