Parent-child communication for screens

[ikarenkov]

Feature description

Parent-child communication is one of the ways to implement communication between screen.
It also can provide flexibility by implementing inversion of control principle, when child doest interacts directly with a parent but provides some set of methods, that parent can interact with.
Common case scenario is when you want to be able to:

1. Observe your children state, to modify your own state. Usecases:
   • Enables button in your parent only if child screen is ready for continue.
2. Triggering some action, f.e. reloading a page.

Challenges

Since our ViewModels are defined in @Composable fun we unable to have direct access to it. There are 2 probably solutions:

1. When we need to interact with ViewModel having only Screen instance, we can try to find ViewModel in our Store and if there is no ViewModel yet - define some default behaviour on client side.
2. Provide the ability to store a ViewModel (or any other object) as a property of Screen.

Tasks

• Provide the way to have VM (or other objects) directly in your Screen
• Provide an example of usage and parent-child communication
• Write a documentation
• Review api of created solutions and simplify it if possible