RxSwift。订阅发生两次

Question

我对RxSwift不够了解，无法独自解决我的问题。我将非常感谢您的帮助。对不起，我的英语。

//declare variables    

var loadedImage = BehaviorRelay<UIImage?>(value: nil)

//Subscribe when creating a cell

loadedImage
            .do(onNext: { (_) in
                cell.activityIndicator.startAnimating()
                cell.activityIndicator.isHidden = false
            })
            .flatMap { (image) -> Observable<String> in
                guard let image = image else { return Observable.just("") }
                return service.uploadPhoto(image: image)
            }
            .observeOn(MainScheduler.instance)
            .subscribeNext { (imageName) in
                vc.createEventData.imageName = imageName

                cell.activityIndicator.stopAnimating()
                cell.activityIndicator.isHidden = true

                let currentPhoto = self.object?.placeholderPhoto
                let image = self.loadedImage.value

                cell.photoEventImageView.image = image == nil ? currentPhoto : image

                if let photoPath = self.object?.photoPath, image == nil {
                    if photoPath != "uploads/photos/.png" {
                        let url = URL(string: "http://test-around.profsoft.online/" + photoPath)
                        cell.photoEventImageView.kf.setImage(with: url)

                        if let r = photoPath.range(of: "/", options: .backwards) {
                            let imageName = photoPath.substring(from: r.upperBound)
                            vc.createEventData.imageName = imageName
                        }
                    }
                }

            }
            .disposed(by: disposeBag)

//I throw a signal when choosing a photo

   func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey: Any]) {
        guard let image = info[.originalImage] as? UIImage else { return }
        loadedImage.accept(image)
        self.viewController?.dismiss(animated: true, completion: nil)
    }

我不明白为什么订阅发生两次。也就是说，我两次进入service.uploadPhoto（图像：图像）。

Answer 1

我只能根据您发布的代码在这里进行推测，但是当单元被重用时，您可能不会取消订阅。因此，由于调用cellForRowAtIndexPath时，disposeBag由ViewController保留，因此您只需添加另一个订阅即可。仅在ViewController被释放后（即DisposeBag被销毁）后，订阅才会被清除。

这是我现在要做的：该单元应该容纳Observable和DisposeBag。您必须在prepareForReuse中清除它：

class YourCell: UITableViewCell {
   var disposeBag = DisposeBag()
   var yourObservable: Observable<UIImage?>?

   func configure(with yourObservable: Observable<UIImage?>) {
      yourObservable = yourObservable
         .subscribe(onNext: /*your code*/ }
         .disposed(by: disposeBag)
   }

   override func prepareForReuse() {
      super.prepareForReuse()
      disposeBag = DisposeBag()
   }
}

然后在您的ViewController中：

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
   let observable = loadedImage /* additional config if needed */
   let cell = tableView.dequeueReusableCell(withIdentifier: "YOUR IDENTIFIER HERE", for: indexPath) as! YourCell
   cell.configure(with: observable)
   return cell
}

此时，您可能还需要考虑您的体系结构。例如，您可以管理可观察到的为单元格提供数据的方式，以便可以将其绑定到表视图，然后让rx管理所有内容。或者，您可以重写TableViewDataSource，以便您的单元可以完全自行处理自己的ViewModel。