无法将数据传递给viewdidload，Swift

Question

i requested data from webserver by alamofire. i want to pass data to viewdidload but data in viewdidload is empty, please help me explain. thanks and sory for my english. this my code

class LiveScoreViewController: UIViewController 
{
   var matchData : JSON! = []

func loadLiveScore(section: String){
    DNService.getLiveScore(section) { (JSON) -> () in
        self.matchData = JSON[ ]

        self.matchData = self.matchData["match"]
        //print(self.matchData) -> is ok
    }
}


override func viewDidLoad() {
    super.viewDidLoad()

    loadLiveScore("LiveScore")

    //print(self.matchData) -> is empty 

}}

Answer 1

If DNService.getLiveScore is a webservice call, then you wont be able to get the matchData inside viewDidLoad, since the webservice call will take some time to complete, whatever you are trying to do with the matchData should be done in the completion block of DNService.getLiveScore most likely

If you want, you can put a print statement right after loadLiveScore in viewDidLoad and also in the completion block, and you will see the order of execution of the print statements is not what you are expecting

Answer 2

getLiveScore is asynchronous method. So you have to use completion handler to get the response. Make an handler for loadLiveScore

func loadLiveScore(section: String), handler: (JSON) -> ()) {

    DNService.getLiveScore(section) { (JSON) -> () in

        handler(JSON) 

    }
}

Call the method from your viewDidLoad as like:

override func viewDidLoad() {
    super.viewDidLoad()

    loadLiveScore("LiveScore") { json in

        print(json) // parse JSON as you need

        self.matchData = json["match"]
    }
}}