* 类型的值没有成员 'rx'

Question

我正在尝试为来自 AlamofireImage 的 ImageDownloader 制作一个小的反应式包装器：

import Foundation
import UIKit.UIImage
import AlamofireImage
import RxCocoa
import RxSwift


extension Reactive where Base: ImageDownloader {

    public func download(urlRequest: URLRequest, filter: ImageFilter?) -> Observable<UIImage> {

        return Observable.create { observer in

            self.base.download(urlRequest, filter: filter) { response in

                if let error = response.error {
                    observer.onError(error)
                } else if let image = response.value {
                    observer.onNext(image)
                }
            }
            return Disposables.create()
        }
    }
}

它编译没有问题。但是，当我尝试在 ImageDownloader 实例上调用 rx.download 时，我收到一条错误消息，指出那里没有“rx”扩展名：

你猜为什么会这样？

Answer 1

您需要先符合ReactiveCompatible 协议，然后才能在您的downloadRequest 调用中使用'rx'

import AlamofireImage
import RxSwift

extension ImageDownloader: ReactiveCompatible {}

extension Reactive where Base: ImageDownloader {

    public func download(urlRequest: URLRequest, filter: ImageFilter?) -> Observable<UIImage> {

        return Observable.create { observer in
            let requestReceipt = ImageDownloader.default.download(urlRequest, filter: filter) { response in
                if let error = response.error {
                    observer.onError(error)
                } else if let image = response.value {
                    observer.onNext(image)
                    observer.onCompleted()
                }
            }
            return Disposables.create {
               requestReceipt?.request.cancel()
            }
        }
    }
}

现在你可以像下面这样调用ImageDownloader.default.rx.download(urlRequest:filter:)方法

let imageRequest = URLRequest.init(url: URL(string: "https://imageserver.com/image/myimage.png")!)
let imageObservable: Observable<UIImage> = ImageDownloader.default.rx.download(urlRequest: imageRequest, filter: nil)