[swift-users] any wisdom about sharing "common" overloads/extensions in base libraries?

Travis Griggs travisgriggs at gmail.com
Tue Jun 20 16:25:54 CDT 2017

> On Jun 20, 2017, at 7:02 AM, David Baraff via swift-users <swift-users at swift.org> wrote:
> I posted this on Apple’s developer forums, and someone suggested trying this here.
> Basically, see https://forums.developer.apple.com/thread/80349 <https://forums.developer.apple.com/thread/80349>
> but in a nutshell: consider that a widely used class/struct (such as CGPoint) is missing some “obvious” functionality [don’t debate that part, just go with it for now], such as the ability to scale a point by a scalar using * as an operator: so in my awesome library “GeometryBase” I write
>   public func * (left: CGPoint, right: double) -> CGPoint {
>       return CGPoint(x: right*left.x, y: right*left.y)
>   }
> Why public?  Well, of course, because I want to use library GeometryBase in many apps or other libraries, and now this overload exists in only one place.
> But other bright people have the same idea, and now I want to use their libraries.  (some of them in my company, some of them not.)
> And now we’re stuck, because everyone is trying to make up for the same (perceived) lack and everyone wants them public so that they don’t have to keep sticking them in each library they write.
> This is not a made up situation: many people even within one company trying to share code somewhat informally are going to write the same code to make using CGPoint/Size/Rect easier, and now we can’t share anything safely.
> Anybody got some good ideas what to do about this?
> [Same question could apply to adding extensions.]

I don’t have a good idea how to solve the problem. We dealt with this type of thing many years ago in Smalltalk systems.

Strategically, when I write application code for end user consumption, I will use my goodly sized library of base library extensions. But when I’m writing a framework to be used by other programmers, I swear off the extensions. If there is an extension that is just so essential, I’ll restrain its scope as much as possible, both with ACLs as well as obvious name prefixes:

	extension CGPoint {
		var radius_myFramework:CGFloat {
			return sqrt((self.x * self.x) + (self.y * self.y))

This doesn’t do much for infix signatures though.

That said, I’m glad to have this problem in Swift. I’m willing to live with the hassle it can create. The gain is worth it. I hate that Python won’t let me extend base types.

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