A UIFont extension to use small caps San Francisco

UIFont+SmallCaps.swift

//
//  UIFont+SmallCaps.swift
//
//  Created by Harshil Shah on 27/04/16.
//  Copyright © 2016 Harshil Shah. All rights reserved.
//

import UIKit

extension UIFont {
    
    class func smallCapsSystemFont(ofSize size: CGFloat, weight: UIFont.Weight = .regular) -> UIFont {
        let descriptor = UIFont.systemFont(ofSize: size, weight: weight).fontDescriptor
        
        let smallLettersToSmallCapsAttribute: [UIFontDescriptor.FeatureKey: Int] = [
            .featureIdentifier: kLowerCaseType,
            .typeIdentifier: kLowerCaseSmallCapsSelector ]
        
        let capitalLettersToSmallCapsAttribute: [UIFontDescriptor.FeatureKey: Int] = [
            .featureIdentifier: kUpperCaseType,
            .typeIdentifier: kUpperCaseSmallCapsSelector ]
        
        let newDescriptor = descriptor.addingAttributes([
            .featureSettings: [
                smallLettersToSmallCapsAttribute,
                capitalLettersToSmallCapsAttribute
            ]
        ])
        
        return UIFont(descriptor: newDescriptor, size: size)
        
    }

}