Managing subscriptions for select

I am getting really confused about some React issues.
I would like to mangage subscriptions for states and cities. I use Ecmascript classes. At first should be subscribed states. After one is chosen, the appropriate cities should be subscribed. How I resolved that, is subscribing them onChange event when selected state.
However it doesn’t seem to be the correct way for me. Code doesn’t look clear. It got even worse, when I added the possibility to edit form and load chosen state and city for it. I have ready somewhere about using sessions. Is it a good idea? Eg:

export default createContainer(() => {

const cities= Meteor.subscribe('city', Session.get("chosenStateId"));
return {
    cities: City.find().fetch(),
    citiesLoaded: states.ready()

}, ProfileLocation);

Could you please explain me how it should be implemented? : adding and editig.
Thanks in advance!