Handy extension to use custom fonts in your iOS Swift application without hardcoding strings.

UIFont+Custom.swift

//
//  UIFont+Custom.swift
//
//  Created by Fernando Ortiz on 10/1/16.
//  Copyright © 2016 Fernando Martín Ortiz. All rights reserved.
//

import UIKit

enum CustomFont: String {
    case firaSansMedium     = "FiraSans-Medium"
    case firaSansRegular    = "FiraSans-Regular"
    case firaSansBold       = "FiraSans-Bold"
}

extension UIFont {
    /**
     Initializes an UIFont using a predefined enumeration and a given size.
     */
    convenience init?(customFont: CustomFont, withSize size: CGFloat) {
        self.init(name: customFont.rawValue, size: size)
    }
}