You mentioned MobX 2.2 action decorator. Do you plan to have any method that will enable to "implement" actions outside of obervable as well? I created an experimental model/wrapper around mobx and I am curious if I could use that feature as well ( https://github.com/pvasek/mobx-app-model ).

Is there any way to hookup to property which is not on the observable yet? Something like this: const store = observable({test1: null }); autorun(() => { console .log(store.test2); }); extendObservable(store, { test2: "aaa" });