iOS swift : Array of Objects conforming to a Protocol: How to check if array contains

Question

我正在尝试实现一个图像下载器类。这是一个单例实现。这个想法是要求实例下载图像并注册为该图像下载的观察者。到目前为止，这是我想出的:

public protocol ImageDownloaderDelegate {
    func imageDownloadFinished(success: Bool)
}

public class ImageDownloader {
    var list: [Int64] = []
    var observer: [Int64:[ImageDownloaderDelegate]] = [:]
    var downloading: Bool = false

    public func downloadImageWithId(immutableId: Int64, delegate: ImageDownloaderDelegate) {
        // Add Id to download list
        if (!contains(list, immutableId)) {
            list.append(immutableId)
        }

        // Add Observer
        var observerList = observer[immutableId]
        if (observerList == nil) {
            observerList = [delegate]
        } else if (!contains(observerList, delegate)) {
            observerList!.append(delegate)
        }
        observer[immutableId] = observerList

        // Start to download
        if (!downloading) {
            self.downloadNextImage()
        }
    }

    private func downloadNextImage() {
        ...
    }

    /// A shared instance of the class
    public class var defaultImageDownloader: ImageDownloader {
        struct Singleton {
            static let instance = ImageDownloader()
        }
        return Singleton.instance
    }
}

我收到以下错误:

“ImageDownloaderDelegate”不能转换为“S.Generator.Element -> L”

非常感谢任何帮助

Answer 1

您没有将正确的参数传递给 contains 函数，该函数需要一个集合和一个谓词(闭包)。

你需要做的

public protocol ImageDownloaderDelegate : class {
    func imageDownloadFinished(success: Bool)
}

public class ImageDownloader {
    var list: [Int64] = []
    var observer: [Int64:[ImageDownloaderDelegate]] = [:]
    var downloading: Bool = false

    public func downloadImageWithId(immutableId: Int64, delegate: ImageDownloaderDelegate) {
        // Add Id to download list
        if (!contains(list, immutableId)) {
            list.append(immutableId)
        }

        // Add Observer
        var observerList = observer[immutableId]
        if (observerList == nil) {
            observerList = [delegate]
        } else if !contains(observerList!, { observer in observer === delegate }) {
            observerList!.append(delegate)
        }
        observer[immutableId] = observerList

        // Start to download
        if (!downloading) {
            self.downloadNextImage()
        }
    }

    private func downloadNextImage() {
        ...
    }

    /// A shared instance of the class
    public class var defaultImageDownloader: ImageDownloader {
        struct Singleton {
            static let instance = ImageDownloader()
        }
        return Singleton.instance
    }
}