I'm not buying this. It basically says "there are a few concepts in Ruby that map nicely to Swift". There are quite a lot of concepts that don't map, for example evaluated classes, which enable things like:

    class Foo
      include Virtus.model

      attribute :foo, String
    end

Now, I could go on like this, but that would be moot. I just question the basic premise of saying that just because 5 features match somewhat nicely (even if it involves more braces of different kinds), those would be reasons for Rubyists to love Swift. Much in contrast, similarity might not be the most compelling reason to switch to something different.