[swift-evolution] Idea: Public Access Modifier Respected in Type Definition

[Jonathan Hull]

+1000

This is the way it always should have worked… and it is the way my brain still expects it to work.  All of the extraneous “Public”s clutter the code and make it much more difficult to read.  Without it, the relatively few properties marked Internal or Private stand out.

I know there is the argument about making people think about whether they want to expose each item… but it doesn’t work that way.  Once you assign someone a rote task (assigning Public to most of the things), you lose the effect of having them think.  From a cognitive psychology lens, when you give the brain a number of decisions to make in a row that are very similar, it will naturally make that task more efficient by automating as much of it as possible (i.e. thinking about it less).  Mistakes become much more likely as a result.

Tl;dr:  Despite the myth/intention that the current setup makes you think about the problem more, it actually does the opposite and leads to an increased risk of error.

Thanks,
Jon


> On Sep 28, 2017, at 10:44 AM, James Valaitis via swift-evolution <swift-evolution at swift.org> wrote:
> 
> When declaring a public class or struct the properties still default to internal.
> ```
> public final class NewType {
> 	/// This property defaults to internal.
> 	var property: Any?
> }
> ```
> 
> This is not the same for a public extension on the type, where then the access modifier is respected for any function or calculated property within the extension.
> ```
> public extension NewType {
> 	/// This function inherits the public modifier.
> 	func function() {
> 	}
> }
> ```
> 
> I dislike this inconsistency, and I frequently find that when using my dynamic frameworks my code will not compile, and it will be due to my accidentally writing a public struct but not declaring the properties public.
> 
> I believe in the idea that explicitly stating the access modifier leads to more legible code, but in my opinion it can be overdone, and I much prefer to explicitly state my intentions in the modifier on the definition or extension. For example:
> 
> ```
> public struct Coordinate {
> 	/// Should default to public.
> 	let latitude: Double
> 	/// Should default to public.
> 	let longitude: Double
> 	/// Should default to public
> 	init?(latitude: Double, longitude: Double) {
> 		guard validate(latitude: latitude, longitude: longitude) else { return nil }
> 		…
> 	}
> }
> internal extension Coordinate {
> 	/// Convenience initialiser to me used internally within the module.
> 	init(coordinate: CLLocationCoordinate2D) {
> 		…
> 	}
> }
> private extension Coordinate {
> 	/// Private validation of the coordinate.
> 	func validate(latitude: Double, longitude: Double) -> Bool {
> 		…
> 	}
> }
> ```
> 
> This is legible and intuitive. The current behaviour is not.
> 
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