Re: [swift-users] Problem with Access Control and Extensions

[Geordie Jay via swift-users]

Adrian Zubarev via swift-users  schrieb am Mi. 20.
Sep. 2017 um 22:13:

> I don’t get your problem here. If you don’t want to debate the correctness
> of your code, why are you asking for help or even showing error messages
> for a code snippet that cannot work?
>
> 1. Drop the access modifier from the extension itself, because this is
> only for convenience, which may or may not rule over the members of the
> extension members. If you’re already explicitly setting the access modifier
> on the extension members then the convenience access modifier makes no
> sense.
> 2. The code cannot work, because you cannot override `viewDidLoad` on a
> class that you don’t own, on a subclass of `UISplitViewController` that
> would be possible.
>

I think the point is that this is possible in ObjcC. So the question is
really whether you can override methods in Swift from classes that are not
your own.

The answer, as far as I’ve seen, is no. Whenever I’ve needed this feature
I’ve used ObjC.

- Geordie



> ```
> class MySplitViewController : UISplitViewController {}
>
> extension MySplitViewController {
> override open func viewDidLoad() {
> super.viewDidLoad()
> /* ... */
> }
> }
> ```
>
>
> Am 20. September 2017 um 21:41:31, Rick Aurbach via swift-users (
> swift-users@swift.org) schrieb:
>
> I am trying to write an extension to a UIKit class, but am running into a
> can’t-win situation:
>
> The code I ‘want’ to write looks like:
>
>
> public extension UISplitViewController {
> override public func viewDidLoad() {
> super.viewDidLoad()
> if UIDevice.current.userInterfaceIdiom == .pad {
> preferredDisplayMode = .automatic
> } else {
> preferredDisplayMode = .primaryOverlay
> }
> }
> }
>
> This generates the error message
>
> /Users/rlaurb/Projects/Cooks-Memory/Cooks-Memory/AppDelegate.swift:131:23:
> Overriding instance method must be as accessible as the declaration it
> overrides
> /Users/rlaurb/Projects/Cooks-Memory/Cooks-Memory/AppDelegate.swift:131:23:
> Overridden declaration is here (UIKit.UIViewController)
>
> But I can’t change the access control of the function to ‘open’, because I
> get the warning that the function can’t be “more” accessible than the
> extension.
>
> And I can’t change the extension’s access to ‘open’ because apparently
> extensions can’t be open.
>
> Now I don’t want to get into a debate about whether this code works — it’s
> just an experiment — but is it even possible to express this idea?? I.e.,
> is it possible to express this idea without subclassing?
>
> Cheers,
>
> Rick Aurbach
>
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Re: [swift-users] Problem with Access Control and Extensions

[Rick Aurbach via swift-users]

Thank you, Adrian. 

(What I meant by “debating the correctness of my code” was that I wanted to 
talk about the approach and not about the content of the viewDidLoad() method.)


Cheers,

Rick Aurbach

> On Sep 20, 2017, at 3:13 PM, Adrian Zubarev  
> wrote:
> 
> I don’t get your problem here. If you don’t want to debate the correctness of 
> your code, why are you asking for help or even showing error messages for a 
> code snippet that cannot work?
> 
> 1. Drop the access modifier from the extension itself, because this is only 
> for convenience, which may or may not rule over the members of the extension 
> members. If you’re already explicitly setting the access modifier on the 
> extension members then the convenience access modifier makes no sense.
> 2. The code cannot work, because you cannot override `viewDidLoad` on a class 
> that you don’t own, on a subclass of `UISplitViewController` that would be 
> possible.
> 
> ```
> class MySplitViewController : UISplitViewController {}
> 
> extension MySplitViewController {
>   override open func viewDidLoad() {
>   super.viewDidLoad()
>   /* ... */
>   }
> }
> ```
> 
> Am 20. September 2017 um 21:41:31, Rick Aurbach via swift-users 
> (swift-users@swift.org ) schrieb:
> 
>> I am trying to write an extension to a UIKit class, but am running into a 
>> can’t-win situation:
>> 
>> The code I ‘want’ to write looks like:
>> 
>> 
>> public extension UISplitViewController {
>> override public func viewDidLoad() {
>> super.viewDidLoad()
>> if UIDevice.current.userInterfaceIdiom == .pad {
>> preferredDisplayMode = .automatic
>> } else {
>> preferredDisplayMode = .primaryOverlay
>> }
>> }
>> }
>> 
>> This generates the error message 
>> /Users/rlaurb/Projects/Cooks-Memory/Cooks-Memory/AppDelegate.swift:131:23: 
>> Overriding instance method must be as accessible as the declaration it 
>> overrides
>> /Users/rlaurb/Projects/Cooks-Memory/Cooks-Memory/AppDelegate.swift:131:23: 
>> Overridden declaration is here (UIKit.UIViewController)
>> 
>> But I can’t change the access control of the function to ‘open’, because I 
>> get the warning that the function can’t be “more” accessible than the 
>> extension.
>> 
>> And I can’t change the extension’s access to ‘open’ because apparently 
>> extensions can’t be open.
>> 
>> Now I don’t want to get into a debate about whether this code works — it’s 
>> just an experiment — but is it even possible to express this idea?? I.e., is 
>> it possible to express this idea without subclassing?
>> 
>> Cheers,
>> 
>> Rick Aurbach
>> 
>> ___
>> swift-users mailing list
>> swift-users@swift.org 
>> https://lists.swift.org/mailman/listinfo/swift-users 
>> 
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Re: [swift-users] Problem with Access Control and Extensions

[Adrian Zubarev via swift-users]

I don’t get your problem here. If you don’t want to debate the correctness of 
your code, why are you asking for help or even showing error messages for a 
code snippet that cannot work?

1. Drop the access modifier from the extension itself, because this is only for 
convenience, which may or may not rule over the members of the extension 
members. If you’re already explicitly setting the access modifier on the 
extension members then the convenience access modifier makes no sense.
2. The code cannot work, because you cannot override `viewDidLoad` on a class 
that you don’t own, on a subclass of `UISplitViewController` that would be 
possible.

```
class MySplitViewController : UISplitViewController {}

extension MySplitViewController {
override open func viewDidLoad() {
super.viewDidLoad()
/* ... */
}
}
```

Am 20. September 2017 um 21:41:31, Rick Aurbach via swift-users 
(swift-users@swift.org) schrieb:

I am trying to write an extension to a UIKit class, but am running into a 
can’t-win situation:

The code I ‘want’ to write looks like:


public extension UISplitViewController {
override public func viewDidLoad() {
super.viewDidLoad()
if UIDevice.current.userInterfaceIdiom == .pad {
preferredDisplayMode = .automatic
} else {
preferredDisplayMode = .primaryOverlay
}
}
}

This generates the error message 
/Users/rlaurb/Projects/Cooks-Memory/Cooks-Memory/AppDelegate.swift:131:23: 
Overriding instance method must be as accessible as the declaration it overrides
/Users/rlaurb/Projects/Cooks-Memory/Cooks-Memory/AppDelegate.swift:131:23: 
Overridden declaration is here (UIKit.UIViewController)

But I can’t change the access control of the function to ‘open’, because I get 
the warning that the function can’t be “more” accessible than the extension.

And I can’t change the extension’s access to ‘open’ because apparently 
extensions can’t be open.

Now I don’t want to get into a debate about whether this code works — it’s just 
an experiment — but is it even possible to express this idea?? I.e., is it 
possible to express this idea without subclassing?

Cheers,

Rick Aurbach

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