Static extension methods in Kotlin

Question

To achieve Uber.doMagic(context), you can write an extension to the companion object of Uber (the companion object declaration is required):

class Uber {
    companion object {}
}

fun Uber.Companion.doMagic(context: Context) { }

This is what the official documentation says:

Kotlin generates static methods for package-level functions. Kotlin can also generate static methods for functions defined in named objects or companion objects if you annotate those functions as @JvmStatic. For example:

Kotlin static methods

class C {
  companion object {
    @JvmStatic fun foo() {}
    fun bar() {}
  }
}

Now, foo() is static in Java, while bar() is not:

C.foo(); // works fine
C.bar(); // error: not a static method

I actually had this exact question 30 minutes ago, so I started digging around and couldn't find any solution or workaround for this, BUT while searching I found this section on the Kotlinglang website that states that:

Note that extensions can be defined with a nullable receiver type. Such extensions can be called on an object variable even if its value is null.

So then I had the craziest idea ever, why not define an extension function with a nullable receiver (without actually using that receiver) and then call it on a null object! So I tried that, and it worked pretty well, but it looked so ugly. It was like this:

(null as Type?).staticFunction(param1, param2)

So I went around that by creating a val in my extensions file of the receiver type that had a value of null and then use it in my other class. So, as an example, here is how I implemented a "static" extension function for the Navigation class in Android: In my NavigationExtensions.kt file:

val SNavigation: Navigation? = null
fun Navigation?.createNavigateOnClickListener(@IdRes resId: Int, args: Bundle? = null, navOptions: NavOptions? = null,
                                                navigationExtras: Navigator.Extras? = null) : (View) -> Unit {
    //This is just implementation details, don't worry too much about them, just focus on the Navigation? part in the method declaration
    return { view: View -> view.navigate(resId, args, navOptions, navigationExtras) }
}

In the code that uses it:

SNavigation.createNavigateOnClickListener(R.id.action_gameWonFragment_to_gameFragment)

Obviously, this isn't a class name, it is just a variable of the class type that has a null value. This is obviously ugly on the extension maker side (because they have to create the variable) and on the developer side (because they have to use the SType format instead of the actual class name), but it is the closest that can be achieved right now compared to actual static functions. Hopefully, the Kotlin language makers will respond to the issue that was created and add that feature in the language.

You can create a static method with using Companion object like:

class Foo {
    // ...
    companion object {
        public fun bar() {
            // do anything
        }
    }
}

and then you can call it like:

class Baz {
    // ...
    private fun callBar() {
        Foo.bar()
    }
}