Overriding methods in Swift extensions

Question

I tend to only put the necessities (stored properties, initializers) into my class definitions and move everything else into their own extension, kind of like a

Answer 1

One of the goals of Swift is static dispatching, or rather the reduction of dynamic dispatching. Obj-C however is a very dynamic language. The situation you're seeing is borne out of the link between the 2 languages and the way they work together. It shouldn't really compile.

One of the main points about extensions is that they are for extending, not for replacing / overriding. It's clear from both the name and the documentation that this is the intention. Indeed if you take out the link to Obj-C from your code (remove NSObject as the superclass) it won't compile.

So, the compiler is trying to decide what it can statically dispatch and what it has to dynamically dispatch, and it's falling through a gap because of the Obj-C link in your code. The reason dynamic 'works' is because it's forcing Obj-C linking on everything so it's all always dynamic.

So, it isn't wrong to use extensions for grouping, that's great, but it is wrong to override in extensions. Any overrides should be in the main class itself, and call out to extension points.