The class enables the UIDebuggingInformationOverlay (which is a private UIWindow subclass). This helps developers and designers debug the app.

KDebugInfoOverlay.swift

//
// Copyright © 2017 Kalpesh Talkar. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
//  For support: https://gist.github.com/KalpeshTalkar/e7769e8875e408806d41cf2eae2ebdf8
//

import UIKit


/// The class enables the UIDebuggingInformationOverlay (which is a private UIWindow subclass)
/// This helps developers and designers debug the app.
class KDebugInfoOverlay {


    /// UIDebuggingInformationOverlay private class
    private static var overlayClass: UIWindow.Type?


    /// Configure and show UIDebuggingInformationOverlay
    public static func configureAndShowDebugInfoOverlay() {
        configureDebugInfoOverlay()
        showDebugInfoOverlay()
    }


    /// Configure UIDebuggingInformationOverlay
    public static func configureDebugInfoOverlay() {
        overlayClass = NSClassFromString("UIDebuggingInformationOverlay") as? UIWindow.Type
        _ = overlayClass?.perform(NSSelectorFromString("prepareDebuggingOverlay"))
    }


    /// Show UIDebuggingInformationOverlay
    public static func showDebugInfoOverlay() {
        // Configure the UIDebuggingInformationOverlay if the class is nil
        if (nil == overlayClass) {
            configureDebugInfoOverlay()
        }
        // Show UIDebuggingInformationOverlay
        let overlay = overlayClass?.perform(NSSelectorFromString("overlay")).takeUnretainedValue() as? UIWindow
        _ = overlay?.perform(NSSelectorFromString("toggleVisibility"))
    }

}