An extension to avoid duplicate subscriptions in UITableCell & UICollectionViewCell

UIReusable+Rx.swift

//
// Created by Johnny on 3/9/2018.
// Copyright (c) 2018 Johnny@Co-fire.com. All rights reserved.
//

import UIKit
import RxCocoa
import RxSwift

private var prepareForReuseBag: Int8 = 0

@objc public protocol Reusable : class {
    func prepareForReuse()
}

extension UITableViewCell: Reusable {}
extension UITableViewHeaderFooterView: Reusable {}
extension UICollectionReusableView: Reusable {}

extension Reactive where Base: Reusable {
    var prepareForReuse: Observable<Void> {
        return Observable.of(sentMessage(#selector(Base.prepareForReuse)).map { _ in }, deallocated).merge()
    }

    var reuseBag: DisposeBag {
        MainScheduler.ensureExecutingOnScheduler()

        if let bag = objc_getAssociatedObject(base, &prepareForReuseBag) as? DisposeBag {
            return bag
        }

        let bag = DisposeBag()
        objc_setAssociatedObject(base, &prepareForReuseBag, bag, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN)

        _ = sentMessage(#selector(Base.prepareForReuse))
                .subscribe(onNext: { [weak base] _ in
                    let newBag = DisposeBag()
                    objc_setAssociatedObject(base, &prepareForReuseBag, newBag, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN)
                })

        return bag
    }
}