# When is the right time to push SE-0068? **URL:** \ **Category:** Discussion\ **Created:** [August 10, 2018, 4:35pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150 "2018-08-10T16:35:54Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![DevAndArtist](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/devandartist/32/287_2.png) [@DevAndArtist](https://forums.swift.org/u/DevAndArtist)\ **Post date:** [August 10, 2018, 4:35pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/1 "2018-08-10T16:35:54Z")
Hi Swift community and all the great devs working on the Swift compiler. I'm wondering when it's finally time to push the implementation of [SE-0068](https://github.com/apple/swift-evolution/blob/master/proposals/0068-universal-self.md) forward? * * * There is a small but very useful pattern I'd like to implement on a base class type. However this pattern requires the missing feature and has no other way to workaround it (except writing the same boilerplate code over and over). ```swift protocol Container : AnyObject { var coordinator: Coordinator { get } } class Base where T : Container { unowned let interface: T init(interface: T) { self.interface = interface } } final class Coordinator : Base where T : Container {} class BaseContainer : Container { private(set) lazy var coordinator = Coordinator(interface: self) ^~~~ } ``` * * * I re-read the rationale of the proposal and if I recall correctly someone said once that the core team decided differently then the stated in the rationale. If I'm not mistaken then there will be no `Self` on value types? (Please correct me if I'm wrong.) I personally would really miss it, but `Self` on classes is better then nothing. ---
**Author:** ![Joe\_Groff](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/joe_groff/32/1929_2.png) [@Joe\_Groff](https://forums.swift.org/u/Joe_Groff)\ **Post date:** [August 10, 2018, 4:41pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/2 "2018-08-10T16:41:34Z")
The main issue here has been the poor representation of `Self` in the compiler. Effectively, dynamic `Self` ought to be treated more like a generic parameter in contexts where it's available, but it's currently treated as a special case in the few places it's supported, which is not a scalable model for generalizing where it can be used. We've made incremental progress in improving the model, but there's still a lot of work to do before this would be practical to implement. ---
**Author:** ![DevAndArtist](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/devandartist/32/287_2.png) [@DevAndArtist](https://forums.swift.org/u/DevAndArtist)\ **Post date:** [August 10, 2018, 5:00pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/3 "2018-08-10T17:00:31Z")
Is this: > [@Joe\_Groff](#): > > the poor representation of `Self` in the compiler anyway important before ABI? By that I mean the things that are missing before the proposal can be implemented will be implemented before or after Swift 5 (not saying that the proposal will be implemented for Swift 5, even if I'd wish for it). ---
**Author:** ![Joe\_Groff](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/joe_groff/32/1929_2.png) [@Joe\_Groff](https://forums.swift.org/u/Joe_Groff)\ **Post date:** [August 10, 2018, 5:01pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/4 "2018-08-10T17:01:59Z")
There shouldn't be any ABI impact. ---
**Author:** ![Moximillian](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/moximillian/32/3055_2.png) [@Moximillian](https://forums.swift.org/u/Moximillian)\ **Post date:** [March 16, 2019, 4:44pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/5 "2019-03-16T16:44:04Z")
Swift 5.1 [https://github.com/apple/swift/pull/22863](https://github.com/apple/swift/pull/22863) ---
**Author:** ![DevAndArtist](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/devandartist/32/287_2.png) [@DevAndArtist](https://forums.swift.org/u/DevAndArtist)\ **Post date:** [March 16, 2019, 4:45pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/6 "2019-03-16T16:45:12Z")
I know already for a couple month, but thank you nevertheless. ---
**Author:** ![Moximillian](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/moximillian/32/3055_2.png) [@Moximillian](https://forums.swift.org/u/Moximillian)\ **Post date:** [March 16, 2019, 4:52pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/7 "2019-03-16T16:52:41Z")
Yeah, I was thinking to have a ”conclusion” to this thread if someone searches for / stumbles upon this topic ---
**Author:** ![johnno1962](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/johnno1962/32/6805_2.png) [@johnno1962](https://forums.swift.org/u/johnno1962)\ **Post date:** [March 18, 2019, 10:51pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/8 "2019-03-18T22:51:03Z")
The implementation has been merged and is available in the [swift.org](https://swift.org/download/#snapshots) nightlies if you want to try it out. ---
**Author:** ![linqingmo](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/linqingmo/32/2442_2.png) [@linqingmo](https://forums.swift.org/u/linqingmo)\ **Post date:** [March 19, 2019, 2:49am UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/9 "2019-03-19T02:49:36Z")
I like SE-0068, but it seems there are still many limits. `Coordinator` is still unsupported. `Self` can't work with generic. That means we can't write `[Self]` or `Self?`. ---
**Author:** ![johnno1962](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/johnno1962/32/6805_2.png) [@johnno1962](https://forums.swift.org/u/johnno1962)\ **Post date:** [March 19, 2019, 2:51pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/10 "2019-03-19T14:51:16Z")
There are limitations that will have to be sorted out with time including Adrian’s example. You should be able to use [Self] as an argument type on a struct however: ```swift struct A { var v = 99 static func b(a: [Self]) { print("Hello, World! \(a)") } func a() { Self.b(a: [Self.init()]) } } ``` For anything else please file a [Jira](https://bugs.swift.org) with example code. ---
**Author:** ![Moximillian](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/moximillian/32/3055_2.png) [@Moximillian](https://forums.swift.org/u/Moximillian)\ **Post date:** [March 19, 2019, 3:13pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/11 "2019-03-19T15:13:14Z")
With the nightly builds, the `as? Self` works great in classes, awesome! Is there already a further ticket for this? ```swift class Foo { func bar(closure: (Self) -> Void) { ... } } ``` ---
**Author:** ![johnno1962](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/johnno1962/32/6805_2.png) [@johnno1962](https://forums.swift.org/u/johnno1962)\ **Post date:** [March 19, 2019, 3:22pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/12 "2019-03-19T15:22:01Z")
I don’t know, feel free to add one. The limitations on Self as a type in method signatures are: only return value if it is a class. See the discussion in [the PR](https://github.com/apple/swift/pull/22863#discussion_r263225089). ---
**Author:** ![hamishknight](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/hamishknight/32/14226_2.png) [@hamishknight](https://forums.swift.org/u/hamishknight)\ **Post date:** [March 19, 2019, 3:23pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/13 "2019-03-19T15:23:30Z")
I filed [SR-10121](https://bugs.swift.org/browse/SR-10121) to track that :) ---
**Author:** ![linqingmo](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/linqingmo/32/2442_2.png) [@linqingmo](https://forums.swift.org/u/linqingmo)\ **Post date:** [March 20, 2019, 1:02am UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/14 "2019-03-20T01:02:42Z")
```swift class A { required init() {} func copy() -> Self { let copy = Self.init() return copy } var copied: Self { let copy = Self.init() return copy } } class B: A { override func copy() -> Self { let copy = super.copy() as! Self // supported return copy } override var copied: Self { let copy = super.copied as! Self // unsupported return copy } } ``` ---
**Author:** ![johnno1962](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/johnno1962/32/6805_2.png) [@johnno1962](https://forums.swift.org/u/johnno1962)\ **Post date:** [March 20, 2019, 1:15pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/15 "2019-03-20T13:15:00Z")
Please file a [Jira](https://bugs.swift.org) for this, include #Self in the title so someone can pick them up. ---
**Author:** ![linqingmo](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/linqingmo/32/2442_2.png) [@linqingmo](https://forums.swift.org/u/linqingmo)\ **Post date:** [March 20, 2019, 3:25pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/16 "2019-03-20T15:25:36Z")
I filed [SR-10135](https://bugs.swift.org/browse/SR-10135). ---
**Author:** ![johnno1962](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/johnno1962/32/6805_2.png) [@johnno1962](https://forums.swift.org/u/johnno1962)\ **Post date:** [March 20, 2019, 3:30pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/17 "2019-03-20T15:30:12Z")
Thanks ---
**Author:** ![johnno1962](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/johnno1962/32/6805_2.png) [@johnno1962](https://forums.swift.org/u/johnno1962)\ **Post date:** [March 29, 2019, 9:04pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/18 "2019-03-29T21:04:54Z")
The fix for [SR-10135](https://bugs.swift.org/browse/SR-10135) merged a couple of days ago and should be available in the [swift.org](https://swift.org/download/#snapshots) nightly builds by now. Please kick the tires and answer on the Jira or PR if you find any problems. ---
**Author:** ![DevAndArtist](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/devandartist/32/287_2.png) [@DevAndArtist](https://forums.swift.org/u/DevAndArtist)\ **Post date:** [April 6, 2019, 5:05pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/19 "2019-04-06T17:05:45Z")
Filed an issues. I am I correct that this limitation exists because it was not yet lifted, otherwise I don't see why properties cannot be of type `Self`. > > > | | | > |------------------|-----------------|… > |Previous ID | SR-10326 | > |Radar | None | > |Original Reporter | @DevAndArtist | > |Type | Bug | > |Status | Resolved | > |Resolution | Done | > > \ > \Environment\ > > DEVELOPMENT-SNAPSHOT-2019-04-04-a > > > \ > > \ > \Additional Detail from JIRA\ > > | | | > |------------------|-----------------| > |Votes | 0 | > |Component/s | Compiler | > |Labels | Bug | > |Assignee | @johnno1962 | > |Priority | Medium | > > > > md5: 00af2a103a18af7ebe8084ad446ae844 > > \ > > > > > > \*\*Issue Description:\*\* > > > This is a strange limitation: > > \`\`\` java > class A { > // okay > func \_self() -\> Self { > return self > } > > // error: 'Self' is only available in a protocol or as the result > // of a method in a class; did you mean 'A'? > var \_\_self: Self { > return self > } > } > \`\`\` ---
**Author:** ![DevAndArtist](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/devandartist/32/287_2.png) [@DevAndArtist](https://forums.swift.org/u/DevAndArtist)\ **Post date:** [April 6, 2019, 5:11pm UTC](https://forums.swift.org/t/when-is-the-right-time-to-push-se-0068/15150/20 "2019-04-06T17:11:25Z")
@johnno1962 since we cannot create nested types in protocols yet, `Self` on classes is the first occurrence of the dynamic type that can be captured by a nested type. Does this mean that nested types are (pseudo-)generic? ```swift class Base { typealias _Self = Self struct PseudoGeneric { var dynamicBase: _Self } } ``` * * * If we could apply this pattern for nested types in protocols one day, this would be awesome.