[swift-evolution] AnyProtocol proposal

[João Nunes]

In the example given. How would you restrict the generic type to a protocol without the use of AnyProtocol ?

Joao

Sent from my iPhone

> On 11 Feb 2016, at 16:53, Developer <devteam.codafi at gmail.com> wrote:
> 
> What are the advantages of using AnyProtocol over a simple `class` constraint?  To my mind, If you're already using Any or AnyObject in an interface, it seems comfortable enough with dynamic dispatch that knowing the underlying representation of the thing you've got won't do you much good.  
> 
> In your specific class, my thinking is a delegate need not be a protocol only if an Object presents just a good a target for a message.
> 
> ~Robert Widmann
> 
> 2016/02/11 9:08、João Nunes via swift-evolution <swift-evolution at swift.org> のメッセージ:
> 
>> Hello,
>> 
>> 
>> 
>> I have been thinking about a case that is missing completely from swift.
>> 
>> 
>> 
>> We have the AnyObject type to represent an Object of any type. 
>> 
>> I recently run upon a situation where i needed a type to represent any Protocol. A AnyProtocol Type would be useful for my case.
>> 
>> 
>> 
>> Example:
>> 
>> 
>> 
>> I have a generic class that needs to receive a protocol type. The code without the AnyProtocol is the following:
>> 
>>  
>> 
>> 
>> 
>> public class MulticastDelegate<T> {
>> 
>> 
>> 
>> 	
>> 
>> 
>> 
>> 	private var delegates = NSHashTable.weakObjectsHashTable()
>> 
>> 
>> 
>> 	
>> 
>> 
>> 
>> 	public init() {}
>> 
>> 
>> 
>> 	
>> 
>> 
>> 
>> 	public func addDelegate(delegate: T) {
>> 
>> 
>> 
>> 		guard delegate is AnyObject else { return }
>> 
>> 
>> 
>> 		delegates.addObject((delegate as! AnyObject))
>> 
>> 
>> 
>> 	}
>> 
>> }
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> This code needs to “trust” that T is a protocol and also make sure T is an Object.
>> 
>> 
>> 
>> 
>> 
>> Example using AnyProtocol, if it existed:
>> 
>> 
>> 
>> public class MulticastDelegate<T:AnyProtocol> {
>> 
>> 
>> 
>> 	
>> 
>> 
>> 
>> 	private var delegates = NSHashTable.weakObjectsHashTable()
>> 
>> 
>> 
>> 	
>> 
>> 
>> 
>> 	public init() {}
>> 
>> 
>> 
>> 	
>> 
>> 
>> 
>> 	public func addDelegate(delegate: T) {
>> 
>> 
>> 
>> 
>> 
>> 		delegates.addObject(delegate)
>> 
>> 
>> 
>> 	}
>> 
>> }
>> 
>> 
>> 
>> Note that the protocol must be a class protocol. This could also be achieved with a where clause or AnyClassProtocol variant.
>> 
>> 
>> 
>> This example is also available on github: https://github.com/jonasman/MulticastDelegate
>> 
>> 
>> 
>> To extend my proposal, there might be cases where AnyStruct and AnyEnum would be usefull. I have no examples for these cases, but i believe someone might have it.
>> 
>> 
>> 
>> What are your thoughts, should I open a PR proposal?
>> 
>> 
>> 
>> 
>> 
>> João Nunes
>> 
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20160217/81867dd5/attachment.html>