> On Jul 2, 2016, at 12:42 AM, L. Mihalkovic <[email protected]>
> wrote:
>
> This is a situation I often run into in jave where I would use an enum to
> create a finite set of constants to be passed (say action identifers). But
> then this makes it very difficult for external modules to extend the core set
> of actions locally. So i generally windup with an enum and an interface (the
> enum implements the interface).
Sure. I would argue that that's the exact right approach to take for this kind
of thing. For instance, for storyboard segue identifiers, I would write
something like this:
open protocol SegueIdentifierProtocol: RawRepresentable where RawValue
== String {}
open protocol SeguePerformable {
associatedtype SegueIdentifier: SegueIdentifierProtocol
// Hooks
func shouldPerformSegue(with identifier: SegueIdentifier,
sender: AnyObject?) -> Bool
func prepare(for segue: UIStoryboardSegue, with identifier:
SegueIdentifier, sender: AnyObject?)
}
public extension SeguePerformable where Self: UIViewController {
// Machinery to bridge to normal UIViewController API
func performSegue(with identifier: SegueIdentifier, sender:
AnyObject?) {...}
override func shouldPerformSegue(withIdentifier identifier:
String, sender: AnyObject?) -> Bool {...}
override func prepare(for segue: UIStoryboardSegue, sender:
AnyObject?) {...}
}
Rather than attempting some sort of universal enum of all identifiers:
extension UIViewController {
open enum SegueIdentifier: String {
// Extensible for users
}
// Hooks
open func shouldPerformSegue(with identifier: SegueIdentifier,
sender: AnyObject?) -> Bool {...}
open func prepare(for segue: UIStoryboardSegue, with
identifier: SegueIdentifier, sender: AnyObject?) {...}
// Machinery to bridge to normal UIViewController API
public func performSegue(with identifier: SegueIdentifier,
sender: AnyObject?) {...}
override public func shouldPerformSegue(withIdentifier
identifier: String, sender: AnyObject?) -> Bool {...}
override public func prepare(for segue: UIStoryboardSegue,
sender: AnyObject?) {...}
}
> Then local extensions are free to define their own local enums to cover only
> their local extensions to the original core set of actions. Then the public
> api definition constrains the action parameter to be
> enum&TheRequiredInterface.
Okay, but why constrain it to `enum`? Do you actually care that it's an `enum`,
or do you just care that there's a type which can give you the identifier you
need? If somebody wrote a highly dynamic client of your code that needed to
generate identifiers on the fly, why should your code reject that?
--
Brent Royal-Gordon
Architechies
_______________________________________________
swift-evolution mailing list
[email protected]
https://lists.swift.org/mailman/listinfo/swift-evolution
