nil target and action? [Resolved]

I managed to get through task 1 of 2 with this code added to "enums.swift":

let done = Button.Done("Done")

..but I have really no idea what type of code is needed for task 2 of 2...?

Was there a swift course that described in detail all about target and action?

A quick google search turned up this old Treehouse blog post (but I think it's pre-Swift):

http://blog.teamtreehouse.com/ios-design-patterns-target-action-part-1

I remember there was a "target-Action link in the Teacher's notes for the Build a Simple iPhone App with Swift course (but of course who ever bothers to click through links in Teacher's Notes ):

https://teamtreehouse.com/library/build-a-simple-iphone-app-with-swift/views-and-view-controllers/view-controllers-and-ibaction

I did find this stackoverflow thread that might be related (shows assigning both target and action):

http://stackoverflow.com/questions/24641350/how-to-set-the-action-for-a-uibarbuttonitem-in-swift

It says the question asked in that thread has to do with this other stackoverflow thread which talks about selectors:

http://stackoverflow.com/questions/24007650/selector-in-swift

Maybe the answer can be found by understanding the answers given in those two stackoverflow threads,

but I certainly didn't see how its related to the 'func color()' code in the "Methods on Enumerations" video:

https://teamtreehouse.com/library/swift-20-enumerations-and-optionals/introduction-to-enumerations/methods-on-enumerations

Also (just for cross reference) there is a related forum thread about that 'func color()' code (which is in the 'SwiftEnumsOptionals-S2' download for the course):

https://teamtreehouse.com/community/i-dont-understand-let-redvalue-let-greenvalue-here

Also found:

There seems to be some documentation to the actual (real) UIStatusBarStyle enumerations ('BlackOpaque', 'BlackTranslucent', 'Default', and 'LightContent') here:

https://developer.xamarin.com/api/type/UIKit.UIStatusBarStyle/