Questions regarding docs, supporting older versions of iOS, and more

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Created Jun ’20

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The session left me with a ton of questions, and I'm not able to find much information in the current documentation.

Note: The session links to an internal page, rather than the live documentation currently (see: "Handling Universal Links")

I will work on filing Feedbacks for many of these, but wanted to present them as questions here as well:

Where is the documentation for the new substitution variables, defaults, case-sensitive and percent-encoded? The docs don't seem to be updated with these features.
How do various versions of the AASA file interact, and how can we specify different versions for different target iOS versions? From the example in the video: They still need the 27mb AASA so long as they must support iOS 13.4 and lower - which for many companies could be 2-3 years!
It's also unclear how the new features might interact with "old" features. If I have an app that supports iOS 12, and want to launch a new app that supports iOS 14+ under the same domain, can the new app use unicode and other new features, or will that break the file for older apps?
How can we test the CDN, and how does cache-invalidation work? This should be documented in detail along with the current information regarding status codes and content-types. Examples of the request/response expected would be helpful as well.
Is .well-known/apple-app-site-association the preferred path now in all cases? The docs seems to suggest this.

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Answer 1

Developer Tools Engineer OP

Apple

Jun ’20

Hi iosdevrecipes! I'll try to answer your questions in order:

Note: The session links to an internal page, rather than the live documentation currently (see: "Handling Universal Links")

I've let our DevPubs team know. Nice catch!

1. Where is the documentation for the new substitution variables, defaults, case-sensitive and percent-encoded? The docs don't seem to be updated with these features.

The documentation isn't quite ready to publish yet. We hope to add it to developer.apple.com shortly.

2. How do various versions of the AASA file interact, and how can we specify different versions for different target iOS versions? From the example in the video: They still need the 27mb AASA so long as they must support iOS 13.4 and lower - which for many companies could be 2-3 years!

iOS will always prefer the most recent data subformat available in an apple-app-site-association file. iOS 12 and earlier are no longer under active development, however adoption of iOS 13 has been fantastic. As of this writing, 92% of iPhones introduced in the last four years are running iOS 13.

3. It's also unclear how the new features might interact with "old" features. If I have an app that supports iOS 12, and want to launch a new app that supports iOS 14+ under the same domain, can the new app use unicode and other new features, or will that break the file for older apps?

Patterns containing non-ASCII Unicode characters will simply be ignored by older versions of iOS, since they always perform percent encoding on URLs before comparing them to patterns.

4. How can we test the CDN, and how does cache-invalidation work? This should be documented in detail along with the current information regarding status codes and content-types. Examples of the request/response expected would be helpful as well.

The CDN's cache is invalidated periodically, however at this time we are not publishing details. If you run into issues or have a specific scenario that you believe we need to support, please let us know via the Feedback Assistant. We'd love to hear from you.

5. Is .well-known/apple-app-site-association the preferred path now in all cases? The docs seems to suggest this.

Yes, it is. The old apple-app-site-association path was deprecated in last year's releases. For more information, see last year's edition of What's new in universal links.

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