Does it possible to override Objective-C methods? ...

# kotlin-native

[Denis Shurygin]

Does it possible to override Objective-C methods? I found way to call them in this document: https://github.com/JetBrains/kotlin-native/blob/master/OBJC_INTEROP.md, but it's not clear of how to override them.

[olonho]

https://github.com/JetBrains/kotlin-native/blob/master/OBJC_INTEROP.md#subclassing-swiftobjective-c-classes-and-protocols-from-kotlin

[Denis Shurygin]

So? The answer is no? I'm not sure that I right understand what is written in this paragraph.

[Denis Shurygin]

Let me explain my question. This document has an example of usage following Objective-C methods.

[player moveTo:LEFT byMeters:17]
[player moveTo:UP byInches:42]

In Objective-c overriding can look as following:

-(void) moveTo:(int)direction byMeters:(double) distance {
...
}

But how do I override them in Kotlin Native?

[AnaR]

I haven't done it yet. But, my guess it it would be how you'd do regular kotlin inheritance. I would try something like:
override fun moveTo(direction:Int, byMeters:double)

[svyatoslav.scherbina]

But, my guess it it would be how you’d do regular kotlin inheritance.

Exactly.

[Denis Shurygin]

I wish so. But it's not working. This two methods have same set of parameters for Kotlin.

override fun moveTo(direction:Int, byMeters:double)
override fun moveTo(direction:Int, byInches:double)

They are equal from Kotlin piont of view. But not for Objective-C in case if you hawe two following methods:

-(void) moveTo:(int)direction byMeters:(double) distance
-(void) moveTo:(int)direction byInches:(double) distance

[svyatoslav.scherbina]

They are equal from Kotlin piont of view.

They are not considered equal in this special case when overriding Objective-C methods.
Have you tried to write such a code?

[Denis Shurygin]

I tried to override following method of UIViewController (iOS UIKit):

func show(_ vc: UIViewController, sender: Any?)

Here is my implementation:

override fun show(vc: UIViewController, sender: Any?)  {
        super.show(vc, sender = sender)
    }

But I faced with 2 errors:
1 string: 'show' overrides nothing
2 string: Unresolved reference: show

I use konan plugin version 0.7.1

[svyatoslav.scherbina]

Yes, because this method is imported to Kotlin as

open external fun showViewController(vc: UIViewController, sender: Any?)

and thus should be called and overridden using this signature.

[Denis Shurygin]

Thank you. Now it work.

[Denis Shurygin]

Could you tell where did you get information about method signature?

[svyatoslav.scherbina]

AppCode should show these signatures.
Also you can get them using klib command-line util:

$ ./bin/klib contents ./klib/platform/ios_arm64/UIKit > log