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 ?? "") 
    } 
  }) 
}