Using custom font for entire iOS app swift

Question

I know that to set a custom font of an element on the screen I can simply dosomeLabel.font=UIFont(name: \"Exo 2.0\", size: 15).

I was wondering how one

Answer 1

The answer is a combination of the answers offered already, but I had to try a combination of things to get it working in iOS 13:

This is all placed in a Table View Controller, which is made to conform to the UIFontPickerViewControllerDelegate in order to offer a view for the user to pick the font. This will update all the UILabels with the new font, but keep the other attributes.

override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    let cell = tableView.cellForRow(at: indexPath)

    if cell === fontCell {
        if #available(iOS 13, *) {
            let configuration = UIFontPickerViewController.Configuration()
            configuration.includeFaces = true

            let fontVC = UIFontPickerViewController(configuration: configuration)
            fontVC.delegate = self

            present(fontVC, animated: true)
        } else {
            let ac = UIAlertController(title: "iOS 13 is required", message: "Custom fonts are only supported by devices running iOS 13 or above.", preferredStyle: .alert)
            ac.addAction(UIAlertAction(title: "OK", style: .default))
            present(ac, animated: true)
        }
    }
}

}

@available(iOS 13.0, *)
extension AppearanceTableViewController: UIFontPickerViewControllerDelegate {
    func fontPickerViewControllerDidPickFont(_ viewController: UIFontPickerViewController) {
        // attempt to read the selected font descriptor, but exit quietly if that fails
        guard let descriptor = viewController.selectedFontDescriptor else { return }

        let font = UIFont(descriptor: descriptor, size: 20)
        UILabel.appearance().substituteFontName = font.fontName
    }
}

extension UILabel {
    @objc public var substituteFontName : String {
        get {
            return self.font.fontName;
        }
        set {
            let fontNameToTest = self.font.fontName.lowercased()
            var fontName = newValue
            if fontNameToTest.range(of: "bold") != nil {
                fontName += "-Bold"
            } else if fontNameToTest.range(of: "medium") != nil {
                fontName += "-Medium"
            } else if fontNameToTest.range(of: "light") != nil {
                fontName += "-Light"
            } else if fontNameToTest.range(of: "ultralight") != nil {
                fontName += "-UltraLight"
            }
            self.font = UIFont(name: fontName, size: self.font.pointSize)
        }
    }
}