No problem, that still works, because the most specific implementation is
chosen:
protocol A { func foo()}
protocol B {} // empty protocol
extension A {
func foo() {
print("Self is A")
}
}
extension A where Self: B {
func foo() {
print("Self is B")
}
}
// Works
struct S1: A, B {}
S1().foo() // Self is B
struct S2: A {}
S2().foo() // Self is A
// Wu's example works, too
struct ThirdParty {
func foo() {
print("Self is ThirdParty")
}
}
extension ThirdParty : A {}
ThirdParty().foo() // Self is ThirdParty
// dynamic dispatch works, too
let a1: A = S1()
a1.foo() // Self is B
let a2: A = S2()
a2.foo() // Self is A
let a3: A = ThirdParty() // Self is ThirdParty
a3.foo()
-Thorsten
> Am 29.04.2016 um 17:20 schrieb Erica Sadun <[email protected]>:
>
> In Wux's example, he has third party code:
>
> ```
> Type ThirdParty {
> func foo() { print("from third party") }
> }
> ```
>
> Then in his own code, he defines protocol A and extends it:
>
> extension A {
> func foo() {
> print("Self is B")
> }
> }
>
> and conforms ThirdParty to A. But he wants the original foo()
> implementation. Your approach
> for writing an extension for plain A without a where clause doesn't offer
> that solution. The goal
> here is "Add this default behavior *only* where a type does not conform to B"
>
> -- E
>
>
>> On Apr 29, 2016, at 9:10 AM, Thorsten Seitz <[email protected]
>> <mailto:[email protected]>> wrote:
>>
>> Just writing an extension for plain A without a where clause works.
>>
>> -Thorsten
>>
>> Am 29.04.2016 um 16:03 schrieb Erica Sadun via swift-evolution
>> <[email protected] <mailto:[email protected]>>:
>>
>>> Gmane is down as far as my browser is concerned and I haven't found
>>> anything by Googling.
>>>
>>> Given the following:
>>>
>>> protocol A {func foo()}
>>> protocol B {} // empty protocol
>>>
>>> extension A where Self:B {
>>> func foo() {
>>> print("Self is B")
>>> }
>>> }
>>>
>>> // Works
>>> struct S1: A, B {}
>>> S1().foo()
>>>
>>> Is there a way to produce a similar extension that exempts any type that
>>> conforms to B?
>>>
>>> cc'ing in Wux because this is a direct response to a scenario he brought up
>>> yesterday.
>>>
>>> -- E
>>>
>>> _______________________________________________
>>> swift-evolution mailing list
>>> [email protected] <mailto:[email protected]>
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>> <https://lists.swift.org/mailman/listinfo/swift-evolution>
>
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