Swift

NSURLSession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。

1，使用Data Task加载数据

使用全局的sharedSession()和dataTaskWithRequest方法创建。

func sessionLoadData(){
    //创建NSURL对象
    let urlString:String="http://hangge.com"
    let url:NSURL! = NSURL(string:urlString)
    //创建请求对象
    let request:NSURLRequest = NSURLRequest(URL: url)
     
    let session = NSURLSession.sharedSession()
   
    let dataTask = session.dataTaskWithRequest(request,
        completionHandler: {(data:NSData!, response:NSURLResponse!, error:NSError!) -> Void in
            if error != nil{
                print(error?.code)
                print(error?.description)
            }else{
                let str = NSString(data: data!, encoding: NSUTF8StringEncoding)
                print(str)
            }
    }) as NSURLSessionTask
     
    //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sharedSession()和downloadTaskWithRequest方法即可

func sessionSimpleDownload(){
    //下载地址
    var url = NSURL(string: "http://hangge.com/blog/images/logo.png")
    //请求
    var request:NSURLRequest = NSURLRequest(URL: url!)
     
    let session = NSURLSession.sharedSession()
     
    //下载任务
    var downloadTask = session.downloadTaskWithRequest(request,
        completionHandler: { (location:NSURL!, response:NSURLResponse!, error:NSError!) -> Void in
            //输出下载文件原来的存放目录
            println("location:(location)")
            //location位置转换
            var locationPath = location.path
            //拷贝到用户目录
            let documnets:String = NSHomeDirectory() + "/Documents/1.png"
            //创建文件管理器
            var fileManager:NSFileManager = NSFileManager.defaultManager()
            fileManager.moveItemAtPath(locationPath!, toPath: documnets, error: nil)
            println("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NSURLSession对象和downloadTaskWithRequest方法

import UIKit
 
class ViewController: UIViewController ,NSURLSessionDownloadDelegate {
 
    override func viewDidLoad() {
        super.viewDidLoad()
         
        sessionSeniorDownload()
    }
     
    //下载文件
    func sessionSeniorDownload(){
        //下载地址
        var url = NSURL(string: "http://hangge.com/blog/images/logo.png")
        //请求
        var request:NSURLRequest = NSURLRequest(URL: url!)
         
        let session = currentSession() as NSURLSession
         
        //下载任务
        var downloadTask = session.downloadTaskWithRequest(request)
         
        //使用resume方法启动任务
        downloadTask.resume()
    }
     
    //创建一个下载模式
    func currentSession() -> NSURLSession{
        var predicate:dispatch_once_t = 0
        var currentSession:NSURLSession? = nil
        
        dispatch_once(&predicate, {
            var config = NSURLSessionConfiguration.defaultSessionConfiguration()
            currentSession = NSURLSession(configuration: config, delegate: self, delegateQueue: nil)
        })
        return currentSession!
    }
     
    //下载代理方法，下载结束
    func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask,
        didFinishDownloadingToURL location: NSURL) {
        //下载结束
        println("下载结束")
         
        //输出下载文件原来的存放目录
        println("location:(location)")
        //location位置转换
        var locationPath = location.path
        //拷贝到用户目录
        let documnets:String = NSHomeDirectory() + "/Documents/1.png"
        //创建文件管理器
        var fileManager:NSFileManager = NSFileManager.defaultManager()
        fileManager.moveItemAtPath(locationPath!, toPath: documnets, error: nil)
        println("new location:(documnets)")
    }
     
    //下载代理方法，监听下载进度
    func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask,
        didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {
        //获取进度
        var written:CGFloat = (CGFloat)(totalBytesWritten)
        var total:CGFloat = (CGFloat)(totalBytesExpectedToWrite)
        var pro:CGFloat = written/total
        println("下载进度：(pro)")
    }
     
    //下载代理方法，下载偏移
    func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask,
        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
    var url = NSURL(string: "http://hangge.com/")
    //请求
    var request:NSURLRequest = NSURLRequest(URL: url!)
     
    let session = NSURLSession.sharedSession()
     
    //上传数据流
    let documents =  NSHomeDirectory() + "/Documents/1.png"
    var imgData = NSData(contentsOfFile: documents)
     
    var uploadTask = session.uploadTaskWithRequest(request, fromData: imgData) {
        (data:NSData!, response:NSURLResponse!, error:NSError!) -> Void in
        //上传完毕后
        println("上传完毕")
    }
     
    //使用resume方法启动任务
    uploadTask.resume()
}