RxSwift 使用小技巧

1、debounce

过滤掉高频产生的元素，例如定位改变时刷新接口,短时间多次调会造成服务器压力过大，可以使用debounce限流，下面例子10s刷新一次

debounce.png

NotificationCenter.default.rx.notification(Notification.Name(rawValue: "kLocationUpdated"))
      .debounce(10, scheduler: MainScheduler.instance)
      .subscribe(onNext: {[weak self] (notification) in
        guard let strongSelf = self else { return }
        // 刷新数据
}).disposed(by: disposeBag)

2、takeUntil

忽略掉在第二个 Observable 产生事件后发出的那部分元素，例如cell进行复用时，忽略之前的订阅

takeUntil.png

先扩展cell的复用序列

extension Reactive where Base: UITableViewCell {
  public var prepareForReuse: RxSwift.Observable {
        var prepareForReuseKey: Int8 = 0
        if let prepareForReuseOB = objc_getAssociatedObject(base, &prepareForReuseKey) as? Observable {
            return prepareForReuseOB
        }
     //将cell复用和deinit转换为序列
        let prepareForReuseOB = Observable.of(
            sentMessage(#selector(Base.prepareForReuse)).map { _ in }
            , deallocated)
            .merge()
        objc_setAssociatedObject(base, &prepareForReuseKey, prepareForReuseOB, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN)

        return prepareForReuseOB
    }
}

takeUntil当cell复用或者销毁cell button 回来复用之前的订阅

cell.button.rx.tap.takeUntil(cell.rx.prepareForReuse)
    .subscribe(onNext: { () in
        print("点击了 \(indexPath)")
    })

3、cell重复订阅问题

除了刚刚上面的takeUntil方法，也可以对cell扩展一个专用DisposeBag

extension Reactive where Base: UITableViewCell {
  public var reuseBag: DisposeBag {
        MainScheduler.ensureExecutingOnScheduler()
        var prepareForReuseBag: Int8 = 0
        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()
                guard let base = base else {return}
                objc_setAssociatedObject(base, &prepareForReuseBag, newBag, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN)
            })
        return bag
    }
}

cell使用扩展的reuseBag 防止重复订阅

cell.button.rx.tap
    .subscribe(onNext: { () in
        print("点击了 \(indexPath)")
    })
    .disposed(by: cell.rx.reuseBag)