Late last year I mentioned a nice introductory tutorial on functional programming with Swift which solves a problem imperatively, and then solves the same problem using functional programming concepts.
Here’s a tutorial from Javier Soto on functional programming in which he goes in-depth describing some functional programming concepts using Swift examples.
In the tutorial Javier explains what a functor is, and using nice example describes what a specific type of functor – the monad – is..
You can find the tutorial on Javier Soto’s blog.
A nice explanation of some commonly seen functional programming concepts.