Based on a talk given at 360iDev 2015. Check out the blog post and video!
You’ve written all kinds of Swift goodness and now want to bring that code over into the Objective-C world. Seeing how well Objective-C makes it into Swift, you’re expecting an equally smooth ride over.
Unfortunately, the default is for nothing in Swift to be visible from Objective-C.
There are two annotations you can add to your types in Swift to access them in Objective-C:
@objc will make them available in Objective-C
dynamic also implies
@objc, and also makes the property or method use Objective-C dynamic dispatch
If you want to swizzle or something, you’ll need to use dynamic; just @objc on its own isn’t enough to guarantee things will use objc_msgSend() as it’s still possible that methods will be devirtualized or inlined.
Of course this will only work for compatible features. If you have a method in your Swift enumeration, that won’t make it over. If you have an enumeration backed by something other than an Int, it won’t make it over.