Cool. Thanks for your comment. Done.
https://bugs.swift.org/browse/SR-5581 <https://bugs.swift.org/browse/SR-5581>
Ray
> On Jul 29, 2017, at 5:55 PM, Slava Pestov <spes...@apple.com> wrote:
>
> What you’re trying to do should be equivalent to this:
>
> protocol Toggling : Equatable {
> …
> }
>
> It’s a bug that placing the constraint on ‘Self’ does not have the same
> effect though; do you mind filing a JIRA?
>
> Slava
>
>> On Jul 29, 2017, at 12:24 PM, Ray Fix via swift-users <swift-users@swift.org
>> <mailto:swift-users@swift.org>> wrote:
>>
>> Hi,
>>
>> I had a question about defining protocols. Originally I wrote:
>>
>> protocol Toggling where Self: Equatable {
>> static var all: [Self] { get }
>> func toggled() -> Self
>> mutating func toggle()
>> }
>>
>> extension Toggling {
>>
>> func toggled() -> Self {
>> let current = Self.all.index(of: self) ?? 0
>> let next = (current + 1) % Self.all.count
>> return Self.all[next]
>> }
>>
>> mutating func toggle() {
>> self = toggled()
>> }
>> }
>>
>> This resulted in a bunch of errors.
>>
>> Playground execution failed:
>> ^
>> error: Toggler.playground:7:28: error: cannot invoke 'index' with an
>> argument list of type '(of: Self)'
>> let current = Self.all.index(of: self) ?? 0
>> ^
>>
>> Toggler.playground:7:28: note: expected an argument list of type '(of:
>> Self.Element)'
>> let current = Self.all.index(of: self) ?? 0
>>
>> This approach worked:
>>
>>
>> protocol Toggling {
>> static var all: [Self] { get }
>> func toggled() -> Self
>> mutating func toggle()
>> }
>>
>> extension Toggling where Self: Equatable {
>>
>> func toggled() -> Self {
>> let current = Self.all.index(of: self) ?? 0
>> let next = (current + 1) % Self.all.count
>> return Self.all[next]
>> }
>>
>> mutating func toggle() {
>> self = toggled()
>> }
>> }
>>
>> This version is probably better anyway but I am wondering if the first
>> approach should have shown an error at the point of trying to attach the
>> constraint to the protocol declaration. Any insights on this?
>>
>> Thank you,
>> Ray Fix
>>
>>
>>
>>
>> _______________________________________________
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>> swift-users@swift.org <mailto:swift-users@swift.org>
>> https://lists.swift.org/mailman/listinfo/swift-users
>
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