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What is a Rx Observable?


RxSwift: Observables

  • Rx Observables are intended for composing flows and sequences of asynchronous data.
  • An Observable is just a sequence with special abilities. For example, it is asynchronous.
  • Observable is a sequence definition that must be subscribed to for anything to really happen.
  • Observables must be defined as being a specific type if the type cannot be inferred.
  • Observables produce events. We say that they are “emitting”.
  • Observables emit next events until an error event or completion event occurs.
  • When an error or completion event occurs, this results in termination and no more events get emitted.
  • An Observer subscribes to an Observable.
  • The Observer reacts to what the Observable emits.
  • Events can contain:
    • Values (Numbers, instances of a custom type).
    • Gesture recognisers (Tap).

Examples of creating observable sequences:

let championsSequence = Observable.just("Celtic")

let titlesInARow = Observable.from([1,2,3,4,5,6,7,8])

Example of subscribing to an observable:

let disposeBag = DisposeBag()

let champions = Observable.just("Celtic!")

champions.subscribe(onNext: { [weak self] champs in
.disposed(by: disposeBag)

Example of a tap event:

  .subscribe(onNext: { [unowned self] in
		self.signIn() })
  .disposed(by: disposeBag)

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