[swift-evolution] [Pitch] Rename `AnyObject` to `AnyClass` and drop current `AnyClass`

Adrian Zubarev adrian.zubarev at devandartist.com
Thu Jun 9 06:23:56 CDT 2016

So what is the counterpart to AnyClass aka. AnyObject.Type for AnyValue? There is no and I don’t see any good name for it.

More confusion with generalized existentials:

Any<class> vs. AnyClass aka AnyObject.Type
Any<class> makes it crystal clear that you’re using an instance of a class not an instance of .Type. It should be consistent.

I’m not proposing for AnyStruct or AnyEnum here, it would be enough to get AnyValue in Swift, but I did considered both in my proposal.

Lets say we also would have something like One<A, B> which picks A or B and we have generalized struct and enum. That said we could create AnyValue like this typealias AnyValue = One<struct, enum>. Again this is not the main part of the proposal.

Adrian Zubarev
Sent with Airmail

Am 9. Juni 2016 um 13:09:28, Patrick Smith (pgwsmith at gmail.com) schrieb:

I find this more confusing, not less. AnyClass suggests that will be any class, but it’s not, it’s any class instance. So I think it’s less accurate.

For arguments that AnyStruct and AnyEnum will come, I don’t agree with those either. AnyValue would make more sense to me. The fact that a value’s type is a struct or enum is irrelevant, just as AnyObject makes no promise about the superclass. I don’t believe there would be much or anything you could do knowing if something was a struct or enum anyway — both support properties and methods, mutations, yet cases can only be used with a concrete enum type. So AFAIK, there would no um value in having both AnyStruct and AnyEnum.

So I am happy staying with AnyObject, as it describes what the actual instance is. And if AnyValue comes, they would pair nicely together.


On 9 Jun 2016, at 8:08 PM, Adrian Zubarev via swift-evolution <swift-evolution at swift.org> wrote:

I added a draft proposal here: https://github.com/DevAndArtist/swift-evolution/blob/rename_anyobject_remove_anyclass/proposals/nnnn-rename-anyobject-remove-anyclass.md

Rename AnyObject and remove current AnyClass

Proposal: SE-NNNN
Author(s): Adrian Zubarev
Status: Awaiting review
Review manager: TBD

From the beginning AnyObject protocol and AnyClass type-alias felt wrong and confusing. This proposal aims to sort out the confusion and provide a consistency for future version of Swift.

Swift-evolution thread: [Pitch] Rename AnyObject to AnyClass and drop current AnyClass


In Swift 3 the standard library will correspond to a particular guideline. This means that the Type suffix will be removed almost everywhere. This provides good readability and makes usage of .Type more clearer and consistent. Furthermore this change is a first step towards consistency for generalized existentials.

Short example:

-func construct(type: AnyClass) -> AnyObject?
+func construct(type: AnyClass.Type) -> AnyClass? {
    if let objectType = type as? NSObject.Type {
        return objectType.init()
    } else {
        return nil
Proposed solution

Remove current AnyClass type-alias from the standard library and rename current AnyObject protocol to AnyClass. Then migrate existing code from AnyClass to AnyClass.Type and from AnyObject to AnyClass.

// Remove completely
-public typealias AnyClass = AnyObject.Type

// Rename to AnyClass
- at objc public protocol AnyObject {}
+ at objc public protocol AnyClass {}
Impact on existing code

This change will break existing code, and will require a migrator to translate Swift 2 code into Swift 3 code.

Alternatives considered & Future consistency

Use generalized existentials with any-class requirement Any<class> instead, which won’t make it into Swift 3 in time:
AnyClass equals Any<class> or typealias AnyClass = Any<class>
AnyClass.Type equals Any<class>.Type
Add AnyValue type-alias with generalized existentials and value keyword:  
AnyValue equals Any<value> or typealias AnyValue = Any<value>
AnyValue.Type equals Any<value>.Type
Or instead AnyValue add AnyStruct and AnyEnum type-aliases:
AnyStruct equals Any<struct> or typealias AnyStruct = Any<struct>
AnyEnum equals Any<enum> or typealias AnyEnum = Any<enum>
AnyStruct.Type equals Any<struct>.Type
AnyEnum.Type equals Any<enum>.Type

// Accept any type that conforms to `SomeProtocol`
func doSomething(with interface: SomeProtocol) { ... }

// Accept any class that conforms to `SomeProtocol`
// We use shorthand syntax for existentials here (SE-0095)
func doSomething(with interfaceReference: AnyClass & SomeProtocol) { ... }
func doSomething(with interfaceReference: Any<class> & SomeProtocol) { ... }

// Accept any value that conforms to `SomeProtocol`
// Missing counterpart to `AnyClass`
func doSomething(with interfaceValue: AnyValue & SomeProtocol) { ... }
func doSomething(with interfaceValue: Any<value> & SomeProtocol) { ... }

// Or more specific value types:
func doSomething(with interfaceValue: AnyStruct & SomeProtocol) { ... }
func doSomething(with interfaceValue: Any<struct> & SomeProtocol) { ... }

func doSomething(with interfaceValue: AnyEnum & SomeProtocol) { ... }
func doSomething(with interfaceValue: Any<enum> & SomeProtocol) { ... }

Adrian Zubarev
Sent with Airmail

swift-evolution mailing list
swift-evolution at swift.org

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20160609/62df60a2/attachment.html>

More information about the swift-evolution mailing list