[swift-users] Overriding properties with limited availability

[Rod Brown]

Jordan,

So sorry, my snippet really wasn’t helpful there! Gah.  I realise the extension wasn’t right! Sorry *facepalm*.

So I have a project. Its deployment target is iOS 10 (because we need 10.0 compatibility for the foreseeable future).

If I add the following code I get errors when it builds:

class MyViewControllerSubclass: UIViewController {
    
    @available(iOS, introduced: 11.0)
    override var additionalSafeAreaInsets: UIEdgeInsets {
        didSet {
            // Need to do work here
        }
    }
    
}



My only solution at this stage is currently to KVO on the AdditionalSafeAreaInsets property, which works, but this seems to point out a language deficiency.


Thanks


> On 3 Aug 2017, at 3:24 am, Jordan Rose <jordan_rose at apple.com> wrote:
> 
> I'm not sure why you're using 'override' in an extension. Did you mean to put that in a subclass? It seems to work for me there.
> 
> Yes, Swift will not let you replace existing methods/properties using an extension if it can statically see that the method/property already exists. (It's not even safe to do that in Objective-C, but the language doesn't stop you.)
> 
> Jordan
> 
> 
>> On Aug 1, 2017, at 22:46, Rod Brown via swift-users <swift-users at swift.org <mailto:swift-users at swift.org>> wrote:
>> 
>> Looks like this is a duplicate of this issue:
>> 
>> https://bugs.swift.org/browse/SR-1486 <https://bugs.swift.org/browse/SR-1486>
>> 
>> I’m curious if anyone knows whether that is actually a bug, or a behavioural choice on Swift’s part?
>> 
>> 
>>> On 2 Aug 2017, at 10:31 am, Rod Brown via swift-users <swift-users at swift.org <mailto:swift-users at swift.org>> wrote:
>>> 
>>> Hi everyone,
>>> 
>>> Something I’ve come across in iOS 11 is that you can’t override properties that are only available on iOS 11 when deploying with a deployment target less than the current target.
>>> 
>>> For example the following code is invalid:
>>> 
>>> extension UIViewController {
>>>     
>>>     @available(iOS, introduced: 11.0)
>>>     open override var additionalSafeAreaInsets: UIEdgeInsets {
>>>         didSet {
>>>             // Do work here only relevant to iOS 11
>>>         }
>>>     }   
>>> }
>>> 
>>> This would be easily overridden in Obj-C, but I can’t do it in Swift. Is there any reason why this limitation exists?
>>> 
>>> Thanks,
>>> 
>>> Rod
>>> _______________________________________________
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>>> swift-users at swift.org <mailto:swift-users at swift.org>
>>> https://lists.swift.org/mailman/listinfo/swift-users <https://lists.swift.org/mailman/listinfo/swift-users>
>> 
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> 

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