Asynchronous programming in Objective-C was never been a truly exciting experience.
We have used delegates for years (I can still remember the first time I’ve seen it, it was around 2001 and I was having fun with Cocoa on my Mac OS X) and not so long ago we have also joined the party of completion handlers.
However both of these processes does not scale well and does not provide a solid error handling mechanism, especially due to some limitations of the language itself (yeah you can do practically anything in C but this is out of the scope of this article).
It’s damn easy to lost yourself in a callback pyramid of doom (also known as callback hell) and generally your code ends up being not so elegant and not so straightforward to read and maintain.
Promises can help us to write better code and, with the help of constructs like await/async it’s really a joy to deal with asynchronous programming.View the article