Why doesn’t this work? ```import Scratch_12.MyUITa...

# announcements

[ribesg]

Why doesn’t this work?

import Scratch_12.MyUITableViewCell.Companion.register

class UITableView

class MyUITableViewCell {
    companion object {
        fun UITableView.register() {}
    }
}

val tableView = UITableView()
with(tableView) {
    MyUITableViewCell.register()
}

The IDE adds the import but the call to register is still red and it says it cannot find it and suggests to import it, which does nothing as it’s already imported (example class names are relevant to the use case).

[ribesg]

My workaround is to rename register to registerMyCell and call tableView.registerMyCell() but I find the way I wrote it in my post to be more clear and better typed

[Rob Elliot]

Should be

import Scratch_12.MyUITableViewCell.Companion.register

class UITableView
class MyUITableViewCell {
    companion object {
        fun UITableView.register() {}
    }
}
val tableView = UITableView()
with(tableView) {
    register()
}

[Rob Elliot]

Within the with block this is the tableView. And register is an extension function on UITableView, so you would normally call it as tableView.register() - so in a with block you call it as just register().

[ribesg]

Yeah but when I have to register 5 different cells I can’t do that, hence my workaround.

[Rob Elliot]

Is this what you want:

class UITableView
class MyUITableViewCell {
    companion object {
        fun register(tableView: UITableView) {}
    }
}
class MyOtherUITableViewCell {
    companion object {
        fun register(tableView: UITableView) { }
    }
}
val tableView = UITableView()
with(tableView) {
    MyUITableViewCell.register(this)
    MyOtherUITableViewCell.register(this)
}

[Rob Elliot]

Are you trying to have multiple fun UITableView.register() extension functions on the companion objects of multiple Cell class companion objects, and get the compiler to disambiguate between them by prefacing the call with the Cell class name?

If so I don’t think that is possible.

[louiscad]

Isn't the issue related to the fact that you're in a scratch file?

[Rob Elliot]

No, it’s exactly the same in normal code.

[ribesg]

Yeah it works the same in normal code. My extension function has 2 receivers, I expected the compiler to disambiguate on both.

[Rob Elliot]

Pretty sure an extension function can only have one receiver. The whole point is that you are pretending to add a function to an existing type in much the same way as if you were editing that type.

[kralli]

You would have to swap your dispatcher and receiver as your method specifies MyUITableViewCell as dispatcher and UITableView as receiver:

class UITableView

class MyUITableViewCell {
    companion object {
        fun UITableView.register() {}
    }
}

val tableView = UITableView()
with(MyUITableViewCell) {
    tableView.register()
}

You are to judge whether or not you like this.

[kralli]

The rules for dispatcher and receiver basically are the following:
• top-level functions like fun example() do not have a dispatcher nor receiver
• extension functions like fun Receiver.example() have an explicit receiver but no dispatcher
• functions of classes like class Receiver { fun example() } have an implicit receiver but no dispatcher
• extension functions in classes like class Dispatcher { fun Receiver.example() } have both an explicit receiver as well as a dispatcher
Dispatchers always have to be bound implicitly (e.g. using with) and receivers specified explicitly (i.e. calling the function on the object).

[ribesg]

Thanks for the explaination @kralli!