Example
Parent value selection
This slider value gets passed down to the child components
Child without state
This child will simply render the value passed into the argument, a redraw will reset it to its parent value.
Child with state
This child will not care about the value passed into the prop, it manages its own state.
Child with state (or update)
This child will update when the passes in a new value, but a redraw will not reset it.
Child with state + key
We can also use the `.key(...)` method to force the component to forget its state, this will however cause the widget to be re-created(a performance penalty).