RxSwift: Subscribing to Observables

• Observables will NOT send events until they have a subscriber.
• It is the subscription that triggers an observable to begin emitting events until .error or .completed is emitted.
• Observing an observable is known as subscribing.
• Subscribe takes an escaping closure that takes an event of the supplied typed (that doesn’t return anything).
• Subscribe returns a Disposable.

let lotteryNumberOne = 1
let lotteryNumberTwo = 2
let lotteryNumberThree = 3

let observable = Observable.of(lotteryNumberOne, lotteryNumberTwo, lotteryNumberThree)

observable.subscribe { element in
	print(element)
}

// next(1)
// next(2)
// next(3)
// completed

• Above emits next events, the below will unwrap the optional elements and produce the value from within the element.

...
observable.subscribe(onNext: { lotteryNumber
	print(lotteryNumber)
})

// 1
// 2
// 3
// NO completed event

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