The simple extension for UIKit animate in RxSwift

RxSwift_animate_extension.swift

import UIKit
import RxSwift
import RxCocoa

struct WRxAnimation {
    let view: UIView
    let transform: CGAffineTransform
}

extension Reactive where Base: UIView {
    
    func animate(withDuration duration: TimeInterval, delay: TimeInterval = 0, options: UIView.AnimationOptions = [], _ transform: CGAffineTransform) -> Observable<WRxAnimation> {
        return Observable.create { obser in
            let newAnimation = base.transform.concatenating(transform)
            UIView.animate(withDuration: duration, delay: delay, options: options, animations: {
                self.base.transform = newAnimation
            }, completion: { _ in
                obser.onNext(WRxAnimation(view: self.base, transform: transform))
                obser.onCompleted()
            })
            return Disposables.create()
        }
    }
    
    func fade(withDuration duration: TimeInterval, delay: TimeInterval = 0) -> Observable<WRxAnimation> {
        return Observable.create { obser in
            UIView.animate(withDuration: duration, delay: delay, animations: {
                self.base.alpha = 0
            }, completion: { _ in
                obser.onNext(WRxAnimation(view: self.base, transform: self.base.transform))
                obser.onCompleted()
            })
            return Disposables.create()
        }
    }
}

extension ObservableType where E == WRxAnimation {
    
    func nextAnimate(withDuration duration: TimeInterval, delay: TimeInterval = 0, _ transform: CGAffineTransform) -> Observable<WRxAnimation> {
        return flatMap { animation -> Observable<AFRxAnimation> in
            let newTransform = animation.transform.concatenating(transform)
            return animation.view.rx.animate(withDuration: duration, delay: delay, newTransform)
        }
    }
    
    func fade(withDuration duration: TimeInterval, delay: TimeInterval = 0) -> Observable<WRxAnimation> {
        return flatMap {
            return $0.view.rx.fade(withDuration: duration, delay: delay)
        }
    }
    
}