Swift Language RxSwift Creating observables
Example
RxSwift offers many ways to create an Observable, let's take a look:
import RxSwift
let intObservale = Observable.just(123) // Observable<Int>
let stringObservale = Observable.just("RxSwift") // Observable<String>
let doubleObservale = Observable.just(3.14) // Observable<Double>
So, the observables are created. They holds just one value and then terminates with success. Nevertheless, nothing happening after it was created. Why?
There are two steps in working with Observables: you observe something to create a stream and then you subscribe to the stream or bind it to something to interact with it.
Observable.just(12).subscribe {
print($0)
}
The console will print:
.Next(12)
.Completed()
And if I interested only in working with data, which take place in .Next events, I'd use subscribeNext operator:
Observable.just(12).subscribeNext {
print($0) // prints "12" now
}
If I want create an observable of many values, I use different operators:
Observable.of(1,2,3,4,5).subscribeNext {
print($0)
}
// 1
// 2
// 3
// 4
// 5
// I can represent existing data types as Observables also:
[1,2,3,4,5].asObservable().subscribeNext {
print($0)
}
// result is the same as before.
And finally, maybe I want an Observable that does some work. For example, it is convenient to wrap a network operation into Observable<SomeResultType>. Let's take a look of do one can achieve this:
Observable.create { observer in // create an Observable ...
MyNetworkService.doSomeWorkWithCompletion { (result, error) in
if let e = error {
observer.onError(e) // ..that either holds an error
} else {
observer.onNext(result) // ..or emits the data
observer.onCompleted() // ..and terminates successfully.
}
}
return NopDisposable.instance // here you can manually free any resources
//in case if this observable is being disposed.
}
