Step 1 - Install XCode 11 and open it.
Step 2 - Select "File" and "New" and "Project" from the main menu.
Step 3 - Select "App" (top left) and Select "Next" (bottom right).
Step 4 - Give your app a name, for User Interface select "Storyboard" and then select "Next".
Step 5 - Select a folder for where to store your new app on your computer and select "Create".
Step 6 - In XCode Navigator (left hand pane) select "Add Files" from the context menu.
Step 7 - Select the folder containing your html/javascript/css/image files - in this example I assume the folder will have the name "www" but it can be anything - just remember to change "www" in the code shown below to what you want.
Step 8 - Select "Create folder references for any added folders" and select "Add"
Step 9 - Select "ViewController.swift" from the Navigator pane and replace everything with with code shown below, changing "www" to the folder name containing your html etc and changing "AppName" to the name of your html file.
Step 10 - Press "Run" and use your new app.
For how to publish it and add other functionality (such as in app purchases) refer to Apple Developer and other internet resources/stack overflow questions.
import Cocoa
import WebKit
class ViewController: NSViewController, WKUIDelegate
{
var webView: WKWebView!
override func loadView()
{
let webConfiguration = WKWebViewConfiguration ();
webConfiguration.preferences.setValue(true, forKey: "allowFileAccessFromFileURLs");
webView = WKWebView (frame: CGRect(x:0, y:0, width:800, height:600), configuration:webConfiguration);
webView.uiDelegate = self ;
view = webView;
}
override func viewDidLoad() {
super.viewDidLoad()
if let url = Bundle.main.url ( forResource: "AppName"
, withExtension: "html"
, subdirectory: "www")
{
let path = url.deletingLastPathComponent();
self.webView.loadFileURL ( url
, allowingReadAccessTo: path);
self.view = webView ;
}
}
}