iOS Swift：符合協議的對象數組：如何檢查數組是否包含

Question

我試圖實現圖像下載類。這是一個單例實現。這個想法是讓實例下載一個圖像並註冊爲該圖像下載的觀察者。這是我想出了迄今：

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 
    } 
} 

我得到以下錯誤：

'ImageDownloaderDelegate' 是無法轉換爲 'S.Generator.Element - > L'

任何幫助非常感謝

Answer 1

您沒有將正確的參數傳遞給contains函數，該函數需要一個集合和一個謂詞（閉包）。

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 
    } 
}