From: Victor Gao <firstname.lastname@example.org>
Subject: Re: [swift-evolution] [swift evolution] [proposal] Proposal to add "implement" keyword to denote protocol method implementation
Date: March 18, 2016 at 21:48:53 ADT
To: Ross O'Brien <email@example.com>
That’s a good point actually, your point about retroactive modeling.
Correct me if I’m wrong, but what you are saying is that if you have a class that has some methods, and then you decided to create a protocol that has the methods of the class. If you want the class to conform to the protocol, you want to be able to do so without having to add the “implement” keyword in front of every method implementation. Is that right?
I also understand that one of the problems with the “implement” keyword: when you create an extension that adds a protocol conformance to a class, if that the class already has the methods defined in the protocol, it wouldn’t work because the methods in the class don’t have the “implement” keyword! This is a perplexing problem.
I recently had the misfortune of deleting what turned out to be a necessary function, because it was an optional requirement of a protocol and wasn't being called by any code in the project, so I would sympathise with this.
On the other hand I've also written protocols composed entirely of functions that an established type already has, so I can retroactively have the type conform. (For example, there's no 'ArithmeticOperation' protocol which Int and Double both conform to, even though they both have a `+ (lhs:Self, rhs:Self) -> Self` operator, so you have to roll your own... unless that should be a proposal itself.) It would be impossible to require a function to use your 'implements' keyword to conform to a protocol in an importing module.
Begin forwarded message:
On Mar 18, 2016, at 21:11, Ross O'Brien <firstname.lastname@example.org> wrote: