func sessionLoadData(){
let urlString:String = "https://api.thinkpage.cn/v3/weather/now.json?key=qc4mshzxtwmicrsa&location=ip&language=zh-Hans&unit=c"
let url1:NSURL! = NSURL(string: urlString)
//创建请求对象
let request:NSURLRequest = NSURLRequest(URL: url1)
let session = NSURLSession.sharedSession()
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)
}
dispatch_semaphore_signal(semaphore)
}) as NSURLSessionTask
//使用resume方法启动任务
dataTask.resume()
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER)
print("数据加载完毕!")
//继续执行其他代码.......
}
sessionLoadData()
这一段代码是怎么用信号量来做到异步获取网络数据的,请大神指导