RxSwift - Create historical observable to see how the data changed

HistoricalObservableExtension.swift

extension Observable {
	func asHistoricalObservable()  -> Observable<(previous: Element, next: Element)> {
		return makeHistoricalObservable(observable: self)
	}
}

extension Variable {
	func asHistoricalObservable()  -> Observable<(previous: Element, next: Element)> {
		return makeHistoricalObservable(observable: self.asObservable())
	}
}

fileprivate func makeHistoricalObservable<E>(observable: Observable<E>) -> Observable<(previous: E, next: E)> {
	return Observable.zip(observable, observable.skip(1)) { (previous: E, next: E) -> (E, E) in
		return (previous: previous, next: next)
	}
}

Usage.swift

let dataForTable = Variable(["Some data", "Goes here", "And changes"])

dataForTable.asHistoricalObservable().subscribe { [weak self] (event) in
	let previous = event.element?.previous ?? []
	let next = event.element?.next ?? []

	print("Previous count - \(previous.count)")
	print("Nex count - \(next.count)")

	// Insert and/or delete rows in table view here
	
}.addDisposableTo(disposeBag)