详解Swift 利用Opration和OprationQueue来下载网络图片

import Foundation import UIKit  public typealias OpreationClosure = ((_ data:Data? , _ error: Error?) -> Void)  class LJOpreationManager: Operation {      /**    * 下载用的url    */   public var imageUrl : String?      /**    * 定义闭包属性,可选类型    */   public var ljcallBackClosure : OpreationClosure?      func initWitParamter(_ url: String, _ callback: @escaping OpreationClosure) -> LJOpreationManager {          if url != ""     {       self.imageUrl = url       self.ljcallBackClosure = callback     }     return self   }      //MARK: -- start   override func start() {          print("start ljManager method")     self.startRequest()   }      func startRequest()   {     //1、创建URL下载地址     let url:URL! = URL(string:self.imageUrl!);          //2、创建Request对象     var urlRequest:URLRequest = URLRequest(url:url);     urlRequest.httpMethod = "GET"     urlRequest.httpShouldUsePipelining = true;          //不需要缓存     //urlRequest.cachePolicy = .reloadIgnoringLocalCacheData          //3、创建会话     let config = URLSessionConfiguration.default     let session = URLSession(configuration: config, delegate:self, delegateQueue: .main)          //4、下载任务     //2>-- -- URLSessionDataDelegate 模式     let loadDataTask = session.dataTask(with: urlRequest)          //5、启动任务     loadDataTask.resume()   }      //初始化一个data，用来存储下载下来的数据   private var _responseData: NSMutableData!   var responseData: NSMutableData!{     get{       if _responseData == nil {         _responseData = NSMutableData()       }       return _responseData     }     set{       self._responseData = newValue     }   } }  // MARK - URLSessionDataDelegate 模式获取数据 extension LJOpreationManager:URLSessionDataDelegate {   @available(iOS 7.0, *)   func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive response: URLResponse, completionHandler: @escaping (URLSession.ResponseDisposition) -> Swift.Void)   {     //允许继续加载数据     completionHandler(.allow)   }      @available(iOS 7.0, *)   func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data)   {     //每次获取的data在此拼装     //print("Data....../(data)")     self.responseData.append(data)          let currentBytes :Float = Float(self.responseData.length)     let allTotalBytes :Float = Float((dataTask.response?.expectedContentLength)!)          let proValu :Float = Float(currentBytes/allTotalBytes)     print("URLSessionDataDelegate----下载进度:------/(proValu*100)%");   }      func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?)   {     if ljcallBackClosure != nil ,let data = self.responseData{              weak var weakSelf : LJOpreationManager? = self       DispatchQueue.main.async         {           print("URLSessionDataDelegate----数据下载完毕")           //将接收的数据结果回调到前台，用于进度展示           weakSelf?.ljcallBackClosure!(data as Data ,nil)       }     }   } } 

import Foundation  class LJWebImageManager: NSObject {      /// Shared manager used .   public static let shared = LJWebImageManager()   public var ljquee = OperationQueue()      override init() {     if #available(iOS 8.0, *) {       self.ljquee.qualityOfService = .background     } else {     }   }      public func requestByUrl(_ url: String,_ callback: @escaping OpreationClosure) -> LJOpreationManager {     let operation = LJOpreationManager().initWitParamter(url, callback)     ljquee.addOperation(operation)          return operation   } } 

func setCellData(_ labelNameStr:String, imageUrlStr:String) {   titleLabel.text = labelNameStr as String   /* Session 的delegate模式下载图片或者数据*/   _ = LJWebImageManager.shared.requestByUrl(imageUrlStr, { (data, error) in          if error == nil, data != nil {       let newImage = UIImage(data: data! as Data)              DispatchQueue.main.async{         let titleImage = UIImageView(frame: CGRect(x: 0, y: 5, width: 40, height: 40))         titleImage.image = newImage         self.contentView.addSubview(titleImage)       }     }     else     {       print(error ?? "")     }   }) }