[swift-evolution] Object declarations

[Kevin Lundberg]

It's an interesting idea, but I have to agree from a not-promoting-singletons standpoint. One can just add a static let to a class to return an instance and make the init private to get similar behavior. 

> On Dec 11, 2015, at 5:55 PM, Jordan Rose via swift-evolution <swift-evolution at swift.org> wrote:
> 
> -1. Enforced singletons lead to code that can't be unit-tested. Local types are occasionally convenient and they can't be unit-tested either, but spending one extra line to name the thing isn't going to hurt. You also can't pick an initializer here (at least not in this version).
> 
> IMHO, this just adds "another kind of thing" just to make code shorter, and "shorter" is not the right goal for Swift.
> 
> Best,
> Jordan
> 
> 
>> On Dec 11, 2015, at 14:07, Marc Knaup via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> Hey guys,
>> 
>> I am working on a proposal which touches (and could even partially depend on) another interesting concept which I think would be a great addition for Swift.
>> 
>> Object declarations could be a way to declare a class or struct with exactly one instance. They are perfect for singletons, anonymous subclasses and to anonymously implement a protocol.
>> 
>> Here some examples how it could look like:
>> 
>> // singleton
>> object GlobalResource {
>>     func doSomething() { … }
>> }
>> 
>> let resource = GlobalResource
>> 
>> // could all be the same
>> resource.doSomething()
>> GlobalResource.doSomething()
>> GlobalResource.Type.doSomething()
>> 
>> 
>> // anonymous subclass
>> class ViewController: UIViewController {
>> 
>>     override func loadView() {
>>         view = object: UIView {
>>             // configure view
>>         }
>>     }
>> }
>> 
>> 
>> // anonymous protocol implementation
>> protocol TapHandler {
>>     func handleTap()
>> }
>> 
>> view.tapHandler = object: TapHandler {
>>     func handleTap() {
>>         // …
>>     }
>> }
>> 
>> 
>> Kotlin is an example for a a modern language which uses this concept:
>> https://kotlinlang.org/docs/reference/object-declarations.html <https://kotlinlang.org/docs/reference/object-declarations.html>
>> 
>> 
>> What do you think about such an addition?
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> 
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