How to suppress `warning: linking against dylib not safe for use in application extensions`?

For your watch/today-widget extension target (so not your app or libray target), go into the project settings and change the build setting APPLICATION_EXTENSION_API_ONLY / Require Only App-Extension-Safe API to NO.

I think you can use embedded framework to share code between your app extension and its containing app. But you have to be careful that your framework doesn't contain apis which are unavailable to extensions. See Some APIs Are Unavailable to App Extensions and Using an Embedded Framework to Share Code.

If your framework doesn't contain such apis don't forget to set Require Only App-Extension-Safe API to YES in your framework target's Build Settings.

As a second way to share source files between application and extension, you don't have to create a separate framework target. You can just share source files by targeting both two projects.

Short answer: there isn't really a way to do.

What I ended up doing was refactoring my code to pull out the pieces that were common to my extension on and my dynamic frame so that my extension could safely reference those pieces independent of the phone-specific code.

I ended up doing this because sometime in the future I will need to submit this to the App Store and Apple's guidelines seem pretty clear that referencing UIApplication is a pretty big no-no.