pod 'UIViewAppearanceSwift'

import UIViewAppearanceSwift

func layout() {
    UINavigationBar.appearanceWhenContained(within: MFMailComposeViewController.self).barStyle = .black
    UIBarButtonItem.appearanceWhenContained(within: UISearchBar.self).setTitleTextAttributes([NSFontAttributeName: UIFont.systemFont(ofSize: 15)], for: .normal)
}