ios reactive-cocoa swift

Getting “use of undeclared type ‘NoError'” with ReactiveCocoa

I am trying to learn ReactiveCocoa and have a hard time getting started. I keep hitting minor bumps as API and tutorials seems to be outdated quickly. Maybe I have the wrong impression.

Just trying to follow this I do not seem to have NoError.

enter image description here

It should be imported correctly, since I have access to Signal, rac_textSignal etc. but I don’t know why NoError is not available.

Their documentation mentions NoError as well but that leads to a 404.

This transition to RAC4 mentions NoError as well. Why is NoError undeclared? I am using ReactiveCocoa 4.0.1.

Edit: I just added public enum NoError : ErrorType {} to the top of the file and it works now. I am not sure if this is a proper solution to the problem though. It is not mentioned in guides and tutorials that I should extend ErrorType myself.