Re: [swift-users] A somewhat stupid question about protocol conformances
Sorry yeah you’re right, the example also requires conditional conformances. If
you do not need dynamic dispatch in your use case then you can workaround the
issue for now by hiding the protocol requirements and abusing the protocol
extension:
import UIKit
protocol AreaProtocol { /* keep it empty */ }
extension AreaProtocol where Self : Sequence, Self.Element == CGPoint {
func area() -> CGFloat {
return 0.0
}
func volume(height: CGFloat) -> CGFloat {
return height * area()
}
}
// or directly
extension Sequence where Element == CGPoint {
// stuff from above
}
extension Array : AreaProtocol {}
let p0 = CGPoint(x: 0.0, y: 0.0)
let p1 = CGPoint(x: 2.0, y: 0.0)
let p2 = CGPoint(x: 2.0, y: 2.0)
let p3 = CGPoint(x: 0.0, y: 2.0)
let poligon = [p0, p1, p2, p3]
let a = poligon.area()
let v = poligon.volume(height: 10.0)
Am 25. November 2017 um 13:58:44, Antonino Ficarra (antonino.fica...@gmail.com)
schrieb:
Adrian,
thanks, but don’t work :-(
import Foundation
protocol AreaProtocol {
// required
func area() -> CGFloat
// implemented in protocol extension
func volume( height:CGFloat ) -> CGFloat
//
}
extension AreaProtocol {
func volume( height:CGFloat ) -> CGFloat {
return height * area()
}
//
//
}
protocol CGPointSequence: Sequence, AreaProtocol where Element == CGPoint {}
extension CGPointSequence {
func area() -> CGFloat {
return 0.0 // ... poligon area
}
}
extension Array:CGPointSequence {} // !'CGPointSequence' requires the types
'Element' and 'CGPoint' be equivalent
Il giorno 25 nov 2017, alle ore 09:11, Adrian Zubarev
ha scritto:
This is correct. None of your types does conform to your protocol because you
never conformance explicitly.
The extenstion you wrote is just a conditional extension which says if the Self
type conforms to AreaProtocol and the associated typed Element is a CGPoint
then add the area method to it. Nothing more, nothing less.
Now you may think that you have to rewrite that extension to `extension
Sequence : AreaProtocol where Element == CGPoint`, but that won't work because
retroactively conforming protocols to other protocols is not supported yet. Nor
are conditional conformances included yet, but they will in Swift 4.1 or 5.
You have one option left.
protocol MySequence : Sequence, AreaProtocol where Element == CGPoint {}
extension Array : MySequence {}
Then also conform other sequences you need to support that functionality.
Double check if the code compiles, I wrote it on my iPhone, but you get the
idea now.
--
Adrian Zubarev
Sent with Airmail
Am 25. November 2017 um 07:40:25, Antonino Ficarra via swift-users
(swift-users@swift.org) schrieb:
In this code example:
import Foundation
protocol AreaProtocol {
func area() -> CGFloat
// implemented in protocol extension
func volume( height:CGFloat ) -> CGFloat
//
}
extension AreaProtocol {
func volume( height:CGFloat ) -> CGFloat {
return height * area()
}
//
//
}
// conform CGPoint sequences to AreaProtocol
extension Sequence
where Self : AreaProtocol, Element == CGPoint
{
func area() -> CGFloat {
return 0.0 // ... poligon area
}
}
let p0 = CGPoint(x: 0.0, y: 0.0)
let p1 = CGPoint(x: 2.0, y: 0.0)
let p2 = CGPoint(x: 2.0, y: 2.0)
let p3 = CGPoint(x: 0.0, y: 2.0)
let poligon = [p0,p1,p2,p3]
let a = poligon.area()// ! Type '[CGPoint]' does not conform to protocol
'AreaProtocol'
let v = poligon.volume( height:10.0 )// ! Value of type '[CGPoint]' has no
member 'volume'
An array of CGPoint is a CGPoint sequence? Why the array don't gets automatic
conformance to AreaProtocol?
How can conform an array of CGPoint to AreaProtocol?
Sorry for my bad english,
Antonino
___
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users
___
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users
Re: [swift-users] A somewhat stupid question about protocol conformances
Adrian,
thanks, but don’t work :-(
import Foundation
protocol AreaProtocol {
// required
funcarea() -> CGFloat
// implemented in protocol extension
funcvolume( height:CGFloat ) -> CGFloat
//
}
extension AreaProtocol {
funcvolume( height:CGFloat ) -> CGFloat {
return height * area()
}
//
//
}
protocol CGPointSequence: Sequence, AreaProtocol where Element == CGPoint {}
extension CGPointSequence {
func area() -> CGFloat {
return 0.0 // ... poligon area
}
}
extension Array:CGPointSequence {} // !'CGPointSequence' requires the types
'Element' and 'CGPoint' be equivalent
> Il giorno 25 nov 2017, alle ore 09:11, Adrian Zubarev
> ha scritto:
>
> This is correct. None of your types does conform to your protocol because you
> never conformance explicitly.
>
> The extenstion you wrote is just a conditional extension which says if the
> Self type conforms to AreaProtocol and the associated typed Element is a
> CGPoint then add the area method to it. Nothing more, nothing less.
>
> Now you may think that you have to rewrite that extension to `extension
> Sequence : AreaProtocol where Element == CGPoint`, but that won't work
> because retroactively conforming protocols to other protocols is not
> supported yet. Nor are conditional conformances included yet, but they will
> in Swift 4.1 or 5.
>
> You have one option left.
> protocol MySequence : Sequence, AreaProtocol where Element == CGPoint {}
>
> extension Array : MySequence {}
>
> Then also conform other sequences you need to support that functionality.
>
> Double check if the code compiles, I wrote it on my iPhone, but you get the
> idea now.
>
> --
> Adrian Zubarev
> Sent with Airmail
> Am 25. November 2017 um 07:40:25, Antonino Ficarra via swift-users
> (swift-users@swift.org ) schrieb:
>
>> In this code example:
>>
>> import Foundation
>>
>> protocol AreaProtocol {
>> func area() -> CGFloat
>>
>> // implemented in protocol extension
>> func volume( height:CGFloat ) -> CGFloat
>> //
>> }
>>
>> extension AreaProtocol {
>> func volume( height:CGFloat ) -> CGFloat {
>> return height * area()
>> }
>> //
>> //
>> }
>>
>>
>> // conform CGPoint sequences to AreaProtocol
>> extension Sequence
>> where Self : AreaProtocol, Element == CGPoint
>> {
>> func area() -> CGFloat {
>> return 0.0 // ... poligon area
>> }
>> }
>>
>> let p0 = CGPoint(x: 0.0, y: 0.0)
>> let p1 = CGPoint(x: 2.0, y: 0.0)
>> let p2 = CGPoint(x: 2.0, y: 2.0)
>> let p3 = CGPoint(x: 0.0, y: 2.0)
>>
>> let poligon = [p0,p1,p2,p3]
>> let a = poligon.area()// ! Type '[CGPoint]' does not conform to protocol
>> 'AreaProtocol'
>> let v = poligon.volume( height:10.0 )// ! Value of type '[CGPoint]' has no
>> member 'volume'
>>
>>
>> An array of CGPoint is a CGPoint sequence? Why the array don't gets
>> automatic conformance to AreaProtocol?
>> How can conform an array of CGPoint to AreaProtocol?
>>
>> Sorry for my bad english,
>> Antonino
>>
>> ___
>> swift-users mailing list
>> swift-users@swift.org
>> https://lists.swift.org/mailman/listinfo/swift-users
___
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users
Re: [swift-users] A somewhat stupid question about protocol conformances
This is correct. None of your types does conform to your protocol because you
never conformance explicitly.
The extenstion you wrote is just a conditional extension which says if the Self
type conforms to AreaProtocol and the associated typed Element is a CGPoint
then add the area method to it. Nothing more, nothing less.
Now you may think that you have to rewrite that extension to `extension
Sequence : AreaProtocol where Element == CGPoint`, but that won't work because
retroactively conforming protocols to other protocols is not supported yet. Nor
are conditional conformances included yet, but they will in Swift 4.1 or 5.
You have one option left.
protocol MySequence : Sequence, AreaProtocol where Element == CGPoint {}
extension Array : MySequence {}
Then also conform other sequences you need to support that functionality.
Double check if the code compiles, I wrote it on my iPhone, but you get the
idea now.
--
Adrian Zubarev
Sent with Airmail
Am 25. November 2017 um 07:40:25, Antonino Ficarra via swift-users
(swift-users@swift.org(mailto:swift-users@swift.org)) schrieb:
> In this code example:
>
> import Foundation
>
> protocol AreaProtocol {
> func area() -> CGFloat
>
> // implemented in protocol extension
> func volume( height:CGFloat ) -> CGFloat
> //
> }
>
> extension AreaProtocol {
> func volume( height:CGFloat ) -> CGFloat {
> return height * area()
> }
> //
> //
> }
>
>
> // conform CGPoint sequences to AreaProtocol
> extension Sequence
> where Self : AreaProtocol, Element == CGPoint
> {
> func area() -> CGFloat {
> return 0.0 // ... poligon area
> }
> }
>
> let p0 = CGPoint(x: 0.0, y: 0.0)
> let p1 = CGPoint(x: 2.0, y: 0.0)
> let p2 = CGPoint(x: 2.0, y: 2.0)
> let p3 = CGPoint(x: 0.0, y: 2.0)
>
> let poligon = [p0,p1,p2,p3]
> let a = poligon.area()// ! Type '[CGPoint]' does not conform to protocol
> 'AreaProtocol'
> let v = poligon.volume( height:10.0 )// ! Value of type '[CGPoint]' has no
> member 'volume'
>
>
> An array of CGPoint is a CGPoint sequence? Why the array don't gets automatic
> conformance to AreaProtocol?
> How can conform an array of CGPoint to AreaProtocol?
>
> Sorry for my bad english,
> Antonino
>
> ___
> swift-users mailing list
> swift-users@swift.org
> https://lists.swift.org/mailman/listinfo/swift-users
___
swift-users mailing list
swift-users@swift.org
https://lists.swift.org/mailman/listinfo/swift-users
