What’s new in Universal Links

What are Universal Links?

• http or https urls that represent your content both in your app and in your website

• they allow users to open content directly in your app instead on in a browser

• created by adding the Associated Domains entitlement in your app and the apple-app-site-association JSON file to your web server.

  • the app entitlement mentions your web server’s domain name, and the web server mentions your app’s application identifier.

New Platform Support: WatchOS

In order to support this, add the Associated Domains entitlement to the WatchKit extension, not the containing WatchKit app.

Since with WatchOS we use WatchKit instead of UIKit, this is how you handle universal links:

// Handling universal links
// WKExtensionDelegate 
func handle(_ userActivity: NSUserActivity) -> Void 

// Opening universal links in other applications
let url = /* ... */ 
WKExtension.shared().openSystemURL(url)

Unlike UIKit, WatchKit’s openSystemURL(:) does not have a callback indicating success or failure: instead, it either succeeds or a pop up error is displayed (shown below).

SwiftUI

Regardless of the platform, you can use handle Universal Links in SwiftUI as well:

// Handling universal links 
onOpenURL { url in /* ... */ } 

// Opening universal links in other applications
@Environment (\.openURL) var openURL 

let url = /* ... */
openURL(url)

Pattern matching

How pattern matching works with Universal Links

You can use the * and ? in your pattern strings to specify wildcards:

• * matches 0 or more characters and does so greedily: it will match as many characters as possible.

• ? matches exactly one character.

• ?* matches at least one character.

New Features

Case insensitive patterns

Available since macOS 10.15.5 and iOS 13.5

"components": [{ "/": "/sourdough/?*", "caseSensitive": false }] 

Unicode patterns

URLs are always ASCII: Unicode characters are turned into ASCII before being part of an URL.

The ASCII representation of Unicode characters completely loses the visual clue of what those characters are, making it completely unreadable.

Thanks to the new percentEncoded key, we can now define a Unicode pattern that is still readable, the conversion to ASCII will automatically be done later.

asciiImage

Defaults

Instead of defining Unicode and case insensitive components for each component, we can define defaults that will be applied to all:

Substitution variables

Available since macOS 10.15.6 and iOS 13.5

• Named list of possible substrings to match against.

• All characters beside $ ( ) are allowed

• Values can contain ? and *

• case-sensitive by default but can be overridden with the caseSensitive key as seen above

Predefined substitution variables:

Usage example:

{
	"applinks": { 
    "substitutionVariables": {
    	"food": [ "burrito", "shawarma", "sushi", "curry-pad-thai" ] 
  	}, 
    "details": [{
      "appIDs": [ "ABCDE12345.com.example.restaurant" ],
      "components": [{ "/"; "/$(lang)_$(region)/$(food)/" }]
    }]
  }
}

We can still exclude individual combinations of variable values:

{
	"applinks": { 
    "substitutionVariables": {
    	"food": [ "burrito", "shawarma", "sushi", "curry-pad-thai" ] 
  	}, 
    "details": [{
      "appIDs": [ "ABCDE12345.com.example.restaurant" ],
      "components": [
	      { "/": "/$(lang)_CA/$(food)/", "exclude": true }, 
	      { "/"; "/$(lang)_$(region)/$(food)/" }
      ]
    }]
  }
}

Apple CDN

Starting with macOS 11 and iOS 14, apps no longer send requests for apple-app-site-association files directly to your web server. Instead, they send these requests to an Apple-managed content delivery network (CDN) dedicated to associated domains.

This way Apple’s CDN can cache those files and make a better experience to the user when their device download your app.

Benefits

Alternate Modes

In case your app/server are not intended to be used publicly, cannot be reached by Apple’s CDN, etc, Apple offers alternate modes:

In the app Associated Domains entitlement we will need to define a url for each mode we would like to operate in, the only requirement (for the non public url) is to have a query item with the name mode and a value specifying the alternate mode to use (developer, managed, or developer+managed)