func loadPM25Data(){
msgLabel.text = "Loding..."
NSURLConnection.sendAsynchronousRequest(NSURLRequest(URL: NSURL(string:"http://aqicn.org/publishingdata/json")!), queue: NSOperationQueue.mainQueue()) { (resp:NSURLResponse?, data:NSData?, error:NSError?) in
do {let jsonArr = try NSJSONSerialization.JSONObjectWithData(data!, options: NSJSONReadingOptions.AllowFragments)
let firstData = (jsonArr as! NSArray).objectAtIndex(0)
let pollutants = firstData.valueForKey("pollutants")
let pm2_5 = (pollutants as! NSArray).objectAtIndex(0)
let theValue = pm2_5.valueForKey("value")
self.msgLabel.text = "PM2.5:\(theValue!)"
}catch{
print("Hello")
}
}
}