uilabel custom positioning with constraints in uipickerview - objective-c

Question

I want to have custom UILabel inside UIPickerView which is right aligned and with width = half of the screen width:
How to position everything with NSConstraints? I had some problems since UILabel was not attached to super view when I have a chance to modify it.
I managed to get it working but it is not done with NSConstraints and is probably wrong (I was able to set up frame if I embeded UILabel inside another view). Any suggestions how to do it properly?
- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view
{
CGFloat width = [UIScreen mainScreen].bounds.size.width;
UIView * newView = [[UIView alloc] init];
UILabel *lbl = [[UILabel alloc] initWithFrame:CGRectMake(0, 0.0f, width / 2 + 18, [pickerView rowSizeForComponent:component].height)];
lbl.text = [self.datasource objectAtIndex:row];
lbl.textAlignment = NSTextAlignmentRight;
lbl.font=[UIFont CPGeneralFontWithSize:22];
[newView addSubview:lbl];
return newView;
}

Answer 1

I don't think there's anything wrong with the way you're adding your label. The view returned by viewForRow:forComponent: is the same width as the picker view by default, so adding the label as a subview is the correct way to get the look you want. If you want to add the label using constraints, you can do it like this,
- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view {
UIView * newView = [[UIView alloc] init];
UILabel *lbl = [[UILabel alloc] init];
lbl.translatesAutoresizingMaskIntoConstraints = NO;
lbl.backgroundColor = [UIColor redColor];
lbl.text = self.datasource[row];
lbl.textAlignment = NSTextAlignmentRight;
lbl.font=[UIFont PGeneralFontWithSize:22];
[newView addSubview:lbl];
[newView addConstraint:[NSLayoutConstraint constraintWithItem:lbl attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:newView attribute:NSLayoutAttributeLeft multiplier:1 constant:0]];
[newView addConstraint:[NSLayoutConstraint constraintWithItem:lbl attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:newView attribute:NSLayoutAttributeWidth multiplier:0.5 constant:0]];
[newView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|[lbl]|" options:0 metrics:nil views:#{#"lbl":lbl}]];
return newView;
}