How to add padding to a NSMutableAttributedString? - ios

Question

I have a label that uses a NSMutableAttributedString to write out the text as:
What I want to do is lower the asterisk's top padding so that it's midY is even with the word Cuisine like below:
How can I add padding using a NSMutableAttributedString?
I know I can create a separate label with the asterisk alone and use anchors w/ a constant to center it but I want to see how this is possible using a NSMutableAttributedString
let cuisineLabel: UILabel = {
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
let attributedText = NSMutableAttributedString(string: "Cuisine ", attributes: [NSAttributedStringKey.font: UIFont.systemFont(ofSize: 17), NSAttributedStringKey.foregroundColor: UIColor.lightGray])
attributedText.append(NSAttributedString(string: "*", attributes: [NSAttributedStringKey.font: UIFont.systemFont(ofSize: 24), NSAttributedStringKey.foregroundColor: UIColor.red]))
label.attributedText = attributedText
return label
}()

Answer 1

The baselineOffset attribute key is used for this purpose.
let cuisine = NSMutableAttributedString(string: "Cuisine")
let asterisk = NSAttributedString(string: "*", attributes: [.baselineOffset: -3])
cuisine.append(asterisk)
Obviously, you will have to calculate the offset using the font size of the rest of the text. This is why I believe that using a full width asterisk (＊) is easier.
Result with full width asterisk (you might want its font size to be a proportion of the font size of the rest of the string):

Answer 2

As Code Different points out, you can do this with baselineOffset attribute. A value of -8 should work for your case:
import UIKit
import PlaygroundSupport
class MyViewController : UIViewController {
override func loadView() {
let view = UIView()
view.backgroundColor = .white
self.view = view
let cuisineLabel: UILabel = {
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
label.frame = CGRect(x: 150, y: 200, width: 200, height: 20)
let attributedText = NSMutableAttributedString(string: "Cuisine ", attributes: [
NSAttributedStringKey.font: UIFont.systemFont(ofSize: 17),
NSAttributedStringKey.foregroundColor: UIColor.lightGray])
attributedText.append(NSAttributedString(string: "*", attributes: [
NSAttributedStringKey.font: UIFont.systemFont(ofSize: 24),
NSAttributedStringKey.baselineOffset: -8,
NSAttributedStringKey.foregroundColor: UIColor.red]))
label.attributedText = attributedText
return label
}()
view.addSubview(cuisineLabel)
}
}
// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()
If you're struggling with line height offsets being messed up because of the new baseline and you're using a multi-line label, try playing with lineHeightMultiple:
let lineStyle = NSParagraphStyle()
lineStyle.lineHeightMultiple = 0.8
...
NSAttributedStringKey.paragraphStyle = style
If not (and you're using multiple labels stacked on top of one another) then you probably just need to adjust the frame of each label in the series to compensate.