swift NSURLSession 使用方法

//NSURLSession
/*
创建一个session ->创建一个task -> 启动task -> 处理回调

*/

//http://www.douban.com/j/app/radio/channels
class ViewController: UIViewController {

override func viewDidLoad() {
        super.viewDidLoad()
       
        let session = NSURLSession.sharedSession()
        let dataTask = session.dataTaskWithURL(NSURL(string: "http://www.douban.com/j/app/radio/channels")!, completionHandler: { (data: NSData?, response: NSURLResponse?, error: NSError?) -> Void in
            //回调处理
            let json = try? NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions()) as! NSDictionary
            print("json:\(json)")
        })
      dataTask.resume()

    }