[swift-evolution] Specify type of a delegate which conforms to a protocol

[Thorsten Seitz]

Thanks for clarifying! In that case I’d prefer Ceylon’s syntax as it seems to express the ideas with less room for confusion (but this probably belongs into another thread). 

-Thorsten


> Am 11.02.2016 um 18:38 schrieb Jordan Rose <jordan_rose at apple.com>:
> 
> No, both Brent and I were proposing replacing the "protocol" in "protocol<UITableViewDelegate, UITableViewDataSource>" with a different word. Brent's word was "all", as in "conforms to all of these"; mine (and JoeG's?) was "any", as in "any type conforming to these". So both of them correspond to Ceylon's "&".
> 
> (The other motivation for "any" or "Any" was by analogy with 'AnyObject' and the existing 'Any'; the latter simply becomes a short form for 'Any<>'.)
> 
> With the word "protocol" no longer in the type, we could then extend it to include a single class bound as well as protocol bounds.
> 
> Jordan
> 
> 
>> On Feb 11, 2016, at 0:39 , Thorsten Seitz <tseitz42 at icloud.com <mailto:tseitz42 at icloud.com>> wrote:
>> 
>> Jordan, I'm not sure if I understood you correctly, do you mean to use  
>> 
>>    all<A, B> for intersection types (Ceylon's A & B), i.e. a type conforming to all listed types 
>>    any<A, B> for union types  (Ceylon's A | B), i.e. a type conforming to any of the listed types
>> 
>> That would be fine, too, I think, while a bit heavier than Ceylon's syntax (though I seem to remember from another thread that there was a problem with using Ceylon's syntax in Swift, though the reason escapes me at the moment).
>> 
>> -Thorsten 
>> 
>>> Am 10.02.2016 um 18:26 schrieb Jordan Rose via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>>:
>>> 
>>> 
>>>>> On Feb 10, 2016, at 5:00 , Brent Royal-Gordon via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>>>> 
>>>>> So, I definitely think there is room for improvement here… how about recycling the inheritance syntax?
>>>>> 
>>>>> let controller: (UIViewController, UITableViewDatasource)
>>>> 
>>>> This declares a tuple containing a UIViewController and a UITableViewDataSource.
>>>> 
>>>>> I added the braces because it would be really when you add the question mark for an optional value; an alternative for this case would be
>>>>> 
>>>>> let controller: Optional<UIViewController, UITableViewDatasource>
>>>> 
>>>> This attempts to declare an optional with two generic types, which doesn't work because Optional only has one type parameter. (But other types, like Dictionary, *do* take two type parameters.)
>>>> 
>>>> Swift does already have a syntax for declaring that a type must conform to two (or more!) protocols:
>>>> 
>>>>   let controller: protocol<UITableViewDataSource, UITableViewDelegate>
>>>> 
>>>> I think this could probably be extended to support one class type as well, perhaps with a new name:
>>>> 
>>>>   let controller: all<UIViewController, UITableViewDataSource>
>>> 
>>> We've been calling it "any" or "Any" (as in "any instance that is-a UIViewController and is-a UITableViewDataSource"), but I think this is the direction we've been talking about over here.
>>> 
>>> (Not that syntax bikeshedding can't still be useful.)
>>> 
>>> Jordan
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> 

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