Does iOS 8 support dynamic linking?
Up until iOS7, Apple did not support dynamic linking due to security concerns. Code reuse between developers usually relied on static libraries, which were built as part of the executable of the app.
Introducing extensions in iOS8 seems to change this a bit, because extensions are separate executables. Sharing code between an extension and its containing app is done via a framework. Apple is saying this in their release notes:
Frameworks for iOS. iOS developers can now create dynamic frameworks. Frameworks are a collection of code and resources to encapsulate functionality that is valuable across multiple projects. Frameworks work perfectly with extensions, sharing logic that can be used by both the main application, and the bundled extensions.
Emphasis is mine.
Further, in the extension dev guide, they explain that you can share code between an extension and the containing app via a "embedded framework".
My question is - what is an embedded framework, how does it differ from a dynamic framework, and will we really see proper dynamic linking in iOS8? All the documentation I've read seems ambiguous about this.
Answer
"Embedded" and "Dynamic" frameworks don't refer to the same aspect of frameworks. They are not the opposite of one another. First, let's define what's a framework: in Apple lingo, a framework refers to some compiled code + the public headers of said code.
Now a dynamic framework is a framework whose code was built as a dynamic library. It is the opposite of a "static" framework, where the code would be built as a static library. In case you're wondering, Wikipedia has a very nice explanation of what's the difference between a static and a dynamic library.
And finally, an embedded framework is a framework that is packaged within an app, as opposed to being installed system-wide, in "/System/Library/Frameworks" for example.