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URLSession 类支持三种类型的任务：加载数据、下载和上传。下面通过样例分别进行介绍。（本文代码已升级至 Swift3）

1，使用Data Task加载数据
使用全局的 URLSession.shared 和 dataTask 方法创建。

func sessionLoadData(){
//创建URL对象
let urlString = "http://hangge.com"
let url = URL(string:urlString)
//创建请求对象
let request = URLRequest(url: url!)

let session = URLSession.shared
let dataTask = session.dataTask(with: request,
    completionHandler: {(data, response, error) -> Void in
        if error != nil{
            print(error.debugDescription)
        }else{
            let str = String(data: data!, encoding: String.Encoding.utf8)
            print(str)
        }
}) as URLSessionTask

  //使用resume方法启动任务
  dataTask.resume()
}

2，使用Download Task来下载文件
（1）不需要获取进度
使用全局的 URLSession.shared 和 downloadTask 方法即可

func sessionSimpleDownload(){
//下载地址
let url = URL(string: "http://hangge.com/blog/images/logo.png")
//请求
let request = URLRequest(url: url!)


let session = URLSession.shared
//下载任务
let downloadTask = session.downloadTask(with: request,
       completionHandler: { (location:URL?, response:URLResponse?, error:Error?)
        -> Void in
        //输出下载文件原来的存放目录
        print("location:\(location)")
        //location位置转换
        let locationPath = location!.path
        //拷贝到用户目录
        let documnets:String = NSHomeDirectory() + "/Documents/1.png"
        //创建文件管理器
        let fileManager = FileManager.default
        try! fileManager.moveItem(atPath: locationPath, toPath: documnets)
        print("new location:\(documnets)")
})


    //使用resume方法启动任务
    downloadTask.resume()
}

（2）实时获取进度
需要使用自定义的 URLSession 对象和 downloadTask 方法

import UIKit

class ViewController: UIViewController, URLSessionDownloadDelegate {


private lazy var session:URLSession = {
    //只执行一次
    let config = URLSessionConfiguration.default
    let currentSession = URLSession(configuration: config, delegate: self,
                                    delegateQueue: nil)
    return currentSession

}()


override func viewDidLoad() {
    super.viewDidLoad()


    sessionSeniorDownload()
}


//下载文件
func sessionSeniorDownload(){
    //下载地址
    let url = URL(string: "http://hangge.com/blog/images/logo.png")
    //请求
    let request = URLRequest(url: url!)


    //下载任务
    let downloadTask = session.downloadTask(with: request)


    //使用resume方法启动任务
    downloadTask.resume()
}



//下载代理方法，下载结束
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask,
                didFinishDownloadingTo location: URL) {
    //下载结束
    print("下载结束")


    //输出下载文件原来的存放目录
    print("location:\(location)")
    //location位置转换
    let locationPath = location.path
    //拷贝到用户目录
    let documnets:String = NSHomeDirectory() + "/Documents/2.png"
    //创建文件管理器
    let fileManager = FileManager.default
    try! fileManager.moveItem(atPath: locationPath, toPath: documnets)
    print("new location:\(documnets)")
}


//下载代理方法，监听下载进度
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask,
                didWriteData bytesWritten: Int64, totalBytesWritten: Int64,
                totalBytesExpectedToWrite: Int64) {
    //获取进度
    let written:CGFloat = (CGFloat)(totalBytesWritten)
    let total:CGFloat = (CGFloat)(totalBytesExpectedToWrite)
    let pro:CGFloat = written/total
    print("下载进度：\(pro)")
}


//下载代理方法，下载偏移
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask,
                didResumeAtOffset fileOffset: Int64, expectedTotalBytes: Int64) {
    //下载偏移，主要用于暂停续传
}


override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}

}

3，使用Upload Task来上传文件

func sessionUpload(){
//上传地址
let url = URL(string: "http://hangge.com/upload.php")
//请求
var request = URLRequest(url: url!, cachePolicy: .reloadIgnoringCacheData)
request.httpMethod = "POST"


let session = URLSession.shared


//上传数据流
let documents =  NSHomeDirectory() + "/Documents/1.png"
let imgData = try! Data(contentsOf: URL(fileURLWithPath: documents))

let uploadTask = session.uploadTask(with: request, from: imgData) {
    (data:Data?, response:URLResponse?, error:Error?) -> Void in
    //上传完毕后
    if error != nil{
        print(error)
    }else{
        let str = String(data: data!, encoding: String.Encoding.utf8)
        print("上传完毕：\(str)")
    }
}

  //使用resume方法启动任务
  uploadTask.resume()
}