"Cannot inherit from non-open class" swift

Question

As of Xcode 8 beta 6 I now get the compile error "Cannot inherit from non-open class (Class)" outside of its defining module"

The class I was inheriting from was part of a separate Swift framework but my project compiled for Xcode 8 beta 5. What do I need to change to get my project to compile again?

Answer 1

Found the answer myself.

In Swift 3 you can now mark a class as open instead of public this allows files outside of the module to subclass that class.

Simply replace public in your module class with open.

Reference here.

Answer 2

The class you inherit from needs to be defined as open instead of public.

A bit more context on the changes to access control in Swift 3:

Swift 2 only had 3 access levels:

• private: entities are available only from within the source file where they are defined.
• internal: entities are available to the entire module that includes the definition.
• public: entities are intended for use as API, and can be accessed by any file that imports the module.

Swift 3 is adding 2 more access levels (open and fileprivate) and changing the meaning of private:

• private: symbol visible within the current declaration only.
• fileprivate: symbol visible within the current file.
• internal: symbol visible within the current module or default access modifier.
• public: symbol visible outside the current module.
• open: for class or function to be subclassed or overridden outside the current module.

Answer 3

I had this error even after marking the class as open (on Xcode 14.1). The fix was a clean (Cmd + Shift + K) and rebuild.