[Interest] Qt/iOS subclassing and/or delegating

[Harri Pasanen]

Compared to C++, Objective-C is very dynamic language and you can do 
many things at runtime.

So you can add methods to existing classes using categories:
https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/ProgrammingWithObjectiveC/CustomizingExistingClasses/CustomizingExistingClasses.html

Or resort to something quite funky to replace existing methods:
https://github.com/rentzsch/jrswizzle

As to your original question, rotation handling is surprisingly tricky 
even in pure Objective-C if you want to conditionally rotate.   For 
instance iOS 8.3 broke some of my code handling that which had worked 
fine since iOS 6, pure Objective-C.

I don't know how Qt hooks into it.

Harri

On 29/05/2015 09:41, Robert Iakobashvili wrote:
> On Fri, May 29, 2015 at 8:38 AM, maitai <maitai at virtual-winds.org> wrote:
>> Thanks Ben for your reply
>>
>> After much digging I made some progress but I am still looking for a way to
>> temporary lock screen auto rotation.
>>
>> I have created my own app delegate to catch openUrl(), and surprisingly it
>> works. I register my app delegate from main.cpp by calling something like
>> this:
>>
>> void QtAppDelegateInitialize ()
>>
>> {
>>
>>      QtAppDelegate *appDelegate = (QtAppDelegate *)[[UIApplication
>> sharedApplication] delegate];
>>
>>      [[UIApplication sharedApplication] setDelegate:[QtAppDelegate
>> sharedQtAppDelegate]];
>>
>>      NSLog(@"Created a new appdelegate");
>>
>> }
>>
>>
>>
>> I then found this very interesting post:
>> https://forum.qt.io/topic/48745/how-to-get-didfinishlaunchingwithoptions-called-in-ios-delegate/7
>> which links to this bug report: QTBUG-38184.
>>
>> First question: I am now wondering how my delegate can possibly work since
>> it seems I can have only one delegate... so what happened to
>> QIOSApplicationDelegate?
>>
>> I then tried various things to add yet another delegate this time based on
>> UINavigationControllerDelegate, but although after much sweat it seems to
>> load, the various methods I am trying to override are never called when I
>> rotate the device.
>>
>> Could it be that I should instead modify/interface QIOSApplicationDelegate
>> itself and not try to create my own delegates?
>>
>> A bit confused at this point, I admit ;)
>>
>> Thanks for any tip
>>
>> Philippe Lelong
>>
>>
>>
>> Le 27-05-2015 20:24, Ben Lau a écrit :
>>
>>
>>
>> On 28 May 2015 at 02:07, maitai <maitai at virtual-winds.org> wrote:
>>> Hello all,
>>>
>>> I've started to port on iOS and need to override some methods, like we
>>> do easily through Java on Qt/Android. I succeeded to implement an
>>> appDelegate in objective-C that works for some events like openURL and
>>> such, but for instance I also need to lock automatic screen rotation in
>>> some circumstances (but not always).
>>
>> Objective-C has a feature to replace the original method of a class. So you
>> may just override the method you needed (In case it don't break Qt)
>> Customizing Existing Classes
>>
>> Example Code:
>> quickios/appdelegate.mm at 0b067e17dc13b8533ca3f7dd574d7e81ea17a015 ·
>> benlau/quickios
>>
>> I have tested to override openURL and didFinishLaunchingWithOptions of
>> AppDelegate with Qt 5.4.1. This method works.
>>
>>> I read that I should somehow override "bool
>>> UINavigationController::shouldRotate()"
>>
>> Never tried. But should be worth to try? I am also be interested with your
>> result.
>>
>>> Should I reimp (subclass?) UINavigationController and how? Or is there a
>>> way to create a new delegate or even better to extend my current
>>> appDelegate?
>>>
>>>
>>> I'm new to Objective-C as you can guess... Any clue would be really
>>> appreciated :)
>>>
>>> Thanks
>>> Philippe Lelong
> Dear Philippe,
>
> Please see the reply Tor Arne inside
>
> https://bugreports.qt.io/browse/QTBUG-42123
>
> That could be an answer - Let it be.
>
> Sincerely,
> Robert
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