I feel like this could be a useful feature. We can right now couple protocols
protocol A { func a() }
protocol B { func b() }
func z(o: protocol<A,B>) {
o.a()
o.b()
}
let o = some as! protocol<A, B>
o.a()
o.b()
But how to be if we need to specify some class/struct in addition to protocol?
So, if this feature could be implemented, I'm +1 on this `type<>` feature
Or probably we can allow class in protocol<>
On 11.05.2016 21:06, Adrian Zubarev via swift-evolution wrote:
Sorry for pushing this back, but I really would like to read any feedback
for this idea of mine. ;)
--
Adrian Zubarev
Sent with Airmail
Am 4. Mai 2016 bei 22:38:33, Adrian Zubarev
(adrian.zuba...@devandartist.com <mailto:adrian.zuba...@devandartist.com>)
schrieb:
This one have bothered me for days, since the idea came to my mind.
I don't want to be too futuristic so here are my first thoughts.
What if Swift 3 would have the ability to merge types and protocols together?
Sure we will see generic typealias in Swift 3 but it doesn't allow us
merge value types which conforms to specific protocols (if there is a need).
protocol SomeProtocol {
func boo()
}
// this use-case can be solved with generic typealias in Swift 3 (at
least for classes), but it is not the only one usecase of type merging
func foo(mergedInstance: type<UIView, SomeProtocol>) {
mergedInstance.removeFromSuperview() // just for the example
mergedInstance.boo()
}
extension UIButton: SomeProtocol { /* implemnt boo() */ }
let button: SomeProtocol = UIButton() // decouple UIButton first
Ok now I want to use one instance as SomeProtocol and UIView.
// another possible use-case
if let mergedView = button as? type<UIView, SomeProtocol> {
mergedView.removeFromSuperview() // just for the example
mergedView.boo()
}
More detailed design:
- type<> can contain only one value or reference type and n protocols
- value or reference type should always be the first type
- type<> should always contain at least 2 types (one value or reference
type and min. one protocol)
- reference types does represent one possible super/base type of the
actuall type
* class A {}
* class B: A {}
* class C: B {}
* possible types for B and C: type<B, AnyProtocolType, ...> or
type<A, AnyProtocolType, ...>
- the dynamicType/Self instance passed to type<> conforms to all
protocols type<> contains
If there is more rules one would apply to this idea feel free to discuss
them here.
--
Adrian Zubarev
Sent with Airmail
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