<div dir="ltr">What about templatetype ? This could also work if we started referring generics as Templates :) and extended them to protocols and functions. <div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sat, Dec 26, 2015 at 3:15 PM, Ross O'Brien <span dir="ltr"><<a href="mailto:narrativium+swift@gmail.com" target="_blank">narrativium+swift@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">There's a problem here because associated types aren't the same as generics.<div><br></div><div>I've been looking this up a lot recently because I've been trying to create a delegate protocol for a generic type. The GenericType<X> requires a GenericTypeDelegate<X> and Swift 2 protocols just don't support those yet; the best workaround of the moment seems to be a wrapper type which wraps the delegate's functions in closures.</div><div><br></div><div>This is a different concept to associated types. I've seen a couple of examples around; the one I'm remembering at the moment involves a protocol for Animals requiring them to have an associated Food type. A Cow could thus be defined as a type implementing the Animal protocol, with an associated type of Grass; this would be very different to an Animal being a generic type, and a Cow being (perhaps typealiased as) an Animal<Grass>. With the associated type, the Cow is known to always eat Grass; with the generic type, every function is written to handle all foodstuffs.</div><div><br></div><div>So, no, the two different syntaxes are required - but protocols with generic parameters (is that the right term for e.g. Grass in Animal<Grass>?) would be a good addition to the language.</div><div><br><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="h5">On Wed, Dec 23, 2015 at 11:06 PM, James Campbell via swift-evolution <span dir="ltr"><<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5"><div dir="ltr">If we made class, structs, protocols and functions use the same generics syntax then I think it would make it more consistent rather than arguing about which keyword to use. I am for-ever being tripped up by lack of generics in the language.<div><br></div><div>class Array<T></div><div>{ </div><div>func first() -> T?</div><div>}</div><div><br></div><div>struct Node<Value></div><div>{</div><div>var value: Value</div><div>}</div><div><br></div><div>Array<Int>()</div><div>Node<Int>()<br></div><div><br></div><div>or</div><div><br></div><div>func makeACell<T>() -> T</div><div>{</div><div>}</div><div><br></div><div>makeACell<MyCell>()</div><div><br></div><div>or</div><div><br></div><div>protocol Collection<Item></div><div>{</div><div>func first() -> Item?</div><div>}</div><div><br></div><div>class IntBag : Collection<Int> //We bind protocol "associated type" using generic syntax when subclassing. In this case we are saying Item should be type Int</div><div>{</div><div>}</div><div><br></div><div>class Array<Item>: Collection<Item> //We bind protocol "associated type" using generic syntax when subclassing. In this case we are saying Item should be the same type as the generic type for Array</div><div>{</div><div>}</div><div><br></div><div>IntBag()</div><div>Array<Int>()</div><div><br></div></div></div></div><div><div><div><div class="h5"><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Dec 23, 2015 at 10:58 PM, James Campbell <span dir="ltr"><<a href="mailto:james@supmenow.com" target="_blank">james@supmenow.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">They are placeholders because in the protocol:<div><br></div><div>prtocotol Collection</div><div>{</div><div> placeholder Item</div><div><br></div><div> func first() -> Item?</div><div> {</div><div> }</div><div>}</div><div><br></div><div>Item is a placeholder for a concrete type, at this moment this is a concept "A collection should return an item of a type" but we don't know what that type is as its a plaeholder for a type.</div><div><br></div><div>therefore in:</div><div><br></div><div>class IntCollection: Collection</div><div>{</div><div> placeholder Item = Int</div><div>}</div><div><br></div><div>We are saying that the placeholder should now become a concrete type. In my eyes associated types are nothing more than generics for protocols which in turn could be argued is some kind of placeholder.</div><div><br></div><div>Associated type means nothing to me, associated to what ? A type could be associated to many things like a variable, or a generic or whatever. A placeholder to mean does what it says on the tin. If we moved to protocols using a syntax closer to generics for classes then I think it would be simpilar to grasp for beginners .</div></div><div class="gmail_extra"><div><div><br><div class="gmail_quote">On Wed, Dec 23, 2015 at 9:35 PM, Jordan Rose <span dir="ltr"><<a href="mailto:jordan_rose@apple.com" target="_blank">jordan_rose@apple.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">James or Erica (or someone else), can you explain what makes these types "placeholders"? I don't think of the other requirements in a protocol as "placeholder properties" or "placeholder methods".<br>
<br>
My explanation of these things is "When a particular type X conforms to a protocol, you can ask about the types that X uses to implement the requirements of the protocol". I guess we could call them "related types" instead of "associated types", but that doesn't seem significantly different.<br>
<span><font color="#888888"><br>
Jordan<br>
</font></span><div><div><br>
<br>
> On Dec 23, 2015, at 12:42, James Campbell via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>> wrote:<br>
><br>
> The thing is associated type means nothing to me, it's too technical. Placeholder type I think would be better even if it's only what we called it in the documentation<br>
><br>
> Sent from my iPhone<br>
<br>
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