angular - get stream of merged observables from another observable in rxjs -

i've simple app which, based on list of cities, retrieves weather information service every x seconds , displays info.

i'm using angular 4 ngrx accomplish , have working, i'd refactor things more reactive.

so piece of code want change:

@effect()   weather$: observable<action> = this.actions$     .oftype(load_weather_action)     .switchmap(() => {       const cityobservables = this.cities.map(city =>         this.service.getweatherbycityid(city.id, city.name)       );       return observable.merge(...cityobservables);     })     .map(weather => new cityweatherloadedaction(weather)); 

so syntax here not important. doing is, every time action of type load_weather_action, create list of observables, 1 each city want data for, , use merge combine them all, , use switchmap replace initial observable stream new one.

all good, if list of cities, instead of simple array, observable? how that?

thanks!

then .switchmap observable, , merge() inside:

weather$: observable<action> = this.actions$     .oftype(load_weather_action)     .switchmap(() => {         return this.cities.switchmap((cities) => {             return observable.merge(...cities.map(city => this.service.getweatherbycityid(city.id, city.name)))         })      })     .map(weather => new cityweatherloadedaction(weather));