custom-URL-handling method not being called

UI Frameworks General
Stoked OP
Created
Replies 12
Boosts 0
Views 733
Participants 4

I've defined a URL scheme for my application, and that's being honored by iOS. But the function that's supposed to handle the URL in my appliation (as documented here) is never called.

The documentation doesn't say exactly where this is supposed to go. I've tried it in my App struct:

@main
struct MyGreatApp: App
{
  var body: some Scene
	{
    WindowGroup
		{
			MainView()
    }
  }

	// Handle custom URLs, specifically the ones sent in invitation E-mails or texts.
	func application(_ application: UIApplication,
					 open theURL: URL,
					 options: [UIApplication.OpenURLOptionsKey : Any] = [:] ) -> Bool
	{
		// Determine who sent the URL.
		let sendingAppID = options[.sourceApplication]
		print("source application = \(sendingAppID ?? "Unknown")")
		...

And I also tried putting this at the file level. No dice either way. Anybody have an idea why?

To head off things I've seen in other posts: I'm not using scenes, and there's no SceneDelegate.

Answered by Stoked in 835320022

So... for anyone who stumbles across this, the final (and a major) problem is that universal links do not work as documented, for two reasons:

  • For unknown reasons, the apple-app-site-association file will not work unless it has a content-type header applied to it by the Web server. This is not automatic and not necessary for any reason other than to work around this issue on Apple's end.

Take a look at this SO question for more info. I'm on Apache, so I used the following in .htaccess

<FilesMatch "apple-app-site-association">
    ForceType application/json
</FilesMatch>

It neglects to mention the need to set up special handling on your Web server to slap an otherwise nonexistent header on this file.

So now my app is receiving universal inks, via the onOpenURL view-modifier. I haven't tried the method that's actually documented as the primary one, in the application delegate yet.

Also, even if I delete and reinstall my app, the user is not asked if he wants to open the link in my app; it just does it.

I encourage everyone to file feedback on the dysfunction of universal links that's due to this unnecessary header requirement.

Replies  12
Boosts 0
Views  733
Participants  4
FPST OP

Have you tried the .onOpenURL modifier? This works for me
Stoked OP

Thanks for the reply. Where would that modifier go?
Stoked OP

So... nobody knows how this is supposed to work? It seems like a pretty significant bug if it doesn't.

DTS Engineer OP
Apple

To receive a Universal Link, use the onOpenURL(perform:) modifier on your root view and you can use [.handlesExternalEvents] (https://developer.apple.com/documentation/swiftui/scene/handlesexternalevents(matching:)) modifier to specify the external events that the view’s scene handles if the scene is already open.
Stoked OP

Thanks for that reply.

Unfortunately, the app still isn't receiving the registered URLs when they're entered in the address bar in Safari. Actually, it's a bit worse than the "custom URL format" attempt, because at least that one prompted me to open the link in my app.

This one just loads the URL like a normal Web page.

I have the apple-app-site-association file in place at my domain, and the entitlements set up in my project. One possible issue is that I don't have an app ID to put into this file. The example shows

"applinks": { "details": [ { "appIDs": [ "ABCDE12345.com.example.app"],

but I only have the equivalent of "com.example.app" in my file because I don't have an app ID. My application isn't finished, and if I upload it to App Store Connect I'm concerned that its identifiers will be impossible to move to a company account that I plan to set up.

Is the missing prepended app ID enough to stop this from working? What's the workaround?

Thanks!

DTS Engineer OP
Apple

@Stoked

Thanks for your question, but I don’t understand exactly, you said:

Unfortunately, the app still isn't receiving the registered URLs

Indeed, you mentioned that you do not have an app finished. Therefore, how can you expect to open an app that does not exist? To accomplish this, you need to create an app and add the app ID into the “applinks” section:

{
    “details”: [
        {
            “appIDs”: [
                “ABCDE12345.com.example.app”
            ]
        }
    ]
}

Once you have completed the app and configured it, you can install it on your device. When the URL is called, following the URL component rules, the installed app will open. If the app is submitted to the store and not installed on the device, the user will be presented with the option to install the app.

I strongly recommend that you finish the app and configure it accordingly.

https://developer.apple.com/documentation/xcode/supporting-universal-links-in-your-app

https://developer.apple.com/documentation/technotes/tn3155-debugging-universal-links

Albert Pascual
  Worldwide Developer Relations.
Stoked OP

Thanks for the reply Albert. I simply said that the app is not finished, so I have not archived it and uploaded it to App Store Connect. It exists, however, and is nearly at a testable state. It builds and runs just fine on devices and simulators, and when I set up a "custom URL" scheme in the project and typed a conforming URL into Safari's address bar (in a simulator), iOS offered to open the URL in my app as expected.

Unfortunately, once the app opened, the documented method for receiving the URL was never called.

Based on the information in this thread, it appears that "custom URLs" may be deprecated or out of favor. So I have now implemented "universal links", following all the steps Apple provides in the document you linked to above. This includes placing the necessary JSON file at a domain I control, and I have confirmed that it's accessible. I also set up entitlements in my project, with "applinks" URLs specified.

In the doc you linked to, the method under "how to handle a universal link in iOS and tvOS" is also never called if I place it in my application struct. I mean this one:

func application(_ application: UIApplication,
                 continue userActivity: NSUserActivity,
                 restorationHandler: @escaping ([UIUserActivityRestoring]?) -> Void) -> Bool

So as recommended in this thread, I put the onOpenURL(perform:) modifier on my root view instead. That doesn't get called either.

Neither of those is surprising, though, because when I go to Safari and enter a URL conforming to one specified in my project's applinks domain entitlements, I am not asked if I want to open the URL in my app (as I used to be with "custom URL scheme").

So the question is why I'm not being asked to open the URL in my app. If I look in my project settings, I do not see an application ID similar to the "ABCDE12345" one in the JSON above. Is that potentially the problem?
Stoked OP

I learned that the correct App-ID prefix is your team identifier. Even putting that in the apple-app-site-association file as the bundle ID prefix did not solve the problem.

Based on the info here (thanks), I learned that you can't use Safari to test the links. So I used Notes.

Still no dice. It doesn't prompt to open the URL in my app. All the necessary files and entitlements appear to be set.
Stoked OP

More undocumented tools are coming out of the woodwork. I have now tried the diagnostic tool that exists on iOS under Developer / Universal Links. That tool confirms that my URL is registered to be handled by my app.

curl was able to retrieve my AASA JSON file from my domain, so at this point there is no apparent reason for this failure.
Stoked OP

So... what workarounds are people using instead of universal links, if any?
Stoked OP
Accepted Answer

So... for anyone who stumbles across this, the final (and a major) problem is that universal links do not work as documented, for two reasons:

  • For unknown reasons, the apple-app-site-association file will not work unless it has a content-type header applied to it by the Web server. This is not automatic and not necessary for any reason other than to work around this issue on Apple's end.

Take a look at this SO question for more info. I'm on Apache, so I used the following in .htaccess

<FilesMatch "apple-app-site-association">
    ForceType application/json
</FilesMatch>

It neglects to mention the need to set up special handling on your Web server to slap an otherwise nonexistent header on this file.

So now my app is receiving universal inks, via the onOpenURL view-modifier. I haven't tried the method that's actually documented as the primary one, in the application delegate yet.

Also, even if I delete and reinstall my app, the user is not asked if he wants to open the link in my app; it just does it.

I encourage everyone to file feedback on the dysfunction of universal links that's due to this unnecessary header requirement.
Stoked OP

Feedback FB17248052 filed against the non-working universal links.