NOT an issue - just an observation, cus something not explicitly mentioned.

[Austin Chen]

Need to add 'dynamic' keyword to the Swift selector, otherwise the selector's DI is not triggered unless being passed to -performSelector

from: Apple
When Swift APIs are imported by the Objective-C runtime, there are no guarantees of dynamic dispatch for properties, methods, subscripts, or initializers. The Swift compiler may still devirtualize or inline member access to optimize the performance of your code, bypassing the Objective-C runtime.

You can use the dynamic modifier to require that access to members be dynamically dispatched through the Objective-C runtime. Requiring dynamic dispatch is rarely necessary. However, it is necessary when using APIs like key–value observing or the method_exchangeImplementations function in the Objective-C runtime, which dynamically replace the implementation of a method at runtime. If the Swift compiler inlined the implementation of the method or devirtualized access to it, the new implementation would not be used.