joining-selector.ts

@State<PreferencesStateModel>({ ... })
export class PreferencesState { ... }

@State<string[]>({ ... })
export class ZooState {

  @Selector([PreferencesState])
  public static firstLocalPanda(state: string[], preferencesState: PreferencesStateModel) {
    return state.find(val => val.indexOf('panda') > -1 && val.indexOf(preferencesState.location));
  }

  @Selector([ZooState.firstLocalPanda])
  public static happyLocalPanda(state: string[], panda: string) {
    return 'happy ' + panda;
  }

}