My RxSwift Summary ③ (What is Observable?)
This article is from My RxSwift Summary ①, My RxSwift Summary② It is a continuation.
What is an Observable?
ʻObservable, ʻobservable sequence, sequence, stream These are all words that have the same meaning and are ** event flow **. (In RxSwift, sequence is often used)
(Quote)
*** Everything is a sequence ***.
Events here include numbers, instances of classes defined by themselves, tap gestures, and so on.
This event is defined by the following ʻEnum`.
Event.swift
public enum Event<Element> {
case next(Element)
case error(Error)
case completed
}
What happens in each case, ʻObservable (sequence)If you look at it with the marble diagram that shows below,  In the case ofnext, ʻObservable emits the next event. It also keeps emitting events until ʻerror / completed` is called.
In case of ʻerror, ʻError is emitted, and ʻobservable` stops the emission of events.
In the case of completed, ʻobservable` is stopped and the event is stopped.
How to process using Observable?
ʻIn order to use the events emitted from Observable, you need to subscribe. (ʻObservable does not emit an event or process with ʻoperator until it is Subscribe) At this time, handlercan be added for each event type. Also, if it isnext, the error instance can be passed to handler if it is ʻElement, and if it is ʻerror`.
Example
Consider the Observable shown in the marble diagram below
Example.swift
let one = "1"
let two = "2"
let three = "3"
let observable = Observable.of(one, two, three)
observable.subscribe { event in
print(event)
}
output
next(1)
next(2)
next(3)
completed
If you subscribe, you will be able to handle events in sequence.
When you print it, next flows 3 times like the output, and finally completed which means stop of ʻobservable` flows.
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