使用NSURLSession同步获取数据（通过添加信号量）

/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()
// 设置信号开始
let semaphore = dispatch_semaphore_create(0)

let dataTask = session.dataTaskWithRequest(request,
    completionHandler: {(data, response, error) -> Void in
        if error != nil{
            print(error?.code)
            print(error?.description)
        }else{
            let str = NSString(data: data!, encoding: NSUTF8StringEncoding)
            print(str)
        }
        //设置信号结束
        dispatch_semaphore_signal(semaphore)
}) as NSURLSessionTask

//使用resume方法启动任务
dataTask.resume()
//等待完成..
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER)
print("数据加载完毕！")
//继续执行其他代码.......