v5 to v6+ migration guide

[jolaf]

Cicerone migration to Kotlin in v6.0 changed the project structure seriously, so code that worked for v5 in many cases can't be formally migrated to v6+, and moreover, sometimes even the proper approach to migration is unclear. It would be nice to have some guide or recommendations on suggested migration strategy.

Personally, I have a v5-based project that was written before me and that I now have to support and improve, and this issue really got me stuck. Any help would be appreciated.

Here are some existing patterns I have trouble migrating:

class MyScreen : SupportAppScreen() {
    override fun getFragment(): Fragment { // New API requires factory
        return MyFragment()
    }
}

class MyNavigator(val activity: FragmentActivity, containerId: Int)
        : SupportAppNavigator(activity, containerId) {
    override fun setupFragmentTransaction(
        command: Command, // Argument missing in v6.0
        currentFragment: Fragment?,
        nextFragment: Fragment?,
        fragmentTransaction: FragmentTransaction
    ) {
    ...
}

[jolaf]

I've found the following solution that seems to work for my case, though I'm not sure if it's fully correct:

class MyScreen : FragmentScreen {
    override fun createFragment(factory: FragmentFactory): Fragment {
        return MyFragment()
    }
}

class MyNavigator(activity: FragmentActivity, containerId: Int)
        : AppNavigator(activity, containerId) {
    private lateinit var command: Command

    override fun applyCommand(command: Command) {
        this.command = command
        super.applyCommand(command)
    }

    override fun setupFragmentTransaction(screen: FragmentScreen, fragmentTransaction: FragmentTransaction, currentFragment: Fragment?, nextFragment: Fragment) {
        ... // Use this.command where command argument was used previously
    }
}

[nikiJava]

@terrakok Excuse me, is it possible to return command to setupFragmentTransaction?