如何在UItextView中添加placeHolder文本？在iphone sdk

#pragma mark -
#pragma mark TextView Delegate methods


    UITextView itsTextView = [[UITextView alloc] initWithFrame:CGRectMake(0,itsTextView.frame.size.width,itsTextView.frame.size.height)];
            [itsTextView setDelegate:self];
            [itsTextView setReturnKeyType:UIReturnKeyDone];
            [itsTextView setText:@"List words or terms separated by commas"];
            [itsTextView setFont:[UIFont fontWithName:@"HelveticaNeue" size:11]];
            [itsTextView setTextColor:[UIColor lightGrayColor]];

- (BOOL) textViewShouldBeginEditing:(UITextView *)textView
{
    if (itsTextView.textColor == [UIColor lightGrayColor]) {
        itsTextView.text = @"";
        itsTextView.textColor = [UIColor blackColor];
    }

    return YES;
}

-(void) textViewDidChange:(UITextView *)textView
{
    if(itsTextView.text.length == 0){
        itsTextView.textColor = [UIColor lightGrayColor];
        itsTextView.text = @"List words or terms separated by commas";
        [itsTextView resignFirstResponder];
    }
}

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text {

    if([text isEqualToString:@"n"]) {
        [textView resignFirstResponder];
        if(itsTextView.text.length == 0){
            itsTextView.textColor = [UIColor lightGrayColor];
            itsTextView.text = @"List words or terms separated by commas";
            [itsTextView resignFirstResponder];
        }
        return NO;
    }

    return YES;
}