Swift get value from api possible threading issue - ios

Question

I have a function that does an api request using google's places api. From the api response data I capture a value and try to set it to a variable. This function is called inside another function. I then try to access that variable but unfortunately the variable doesn't contain the value yet. This appears to be a threading issue but I don't know how to fix it.
update:
I have updated the code based on the responses. Unfortunately I am still not able to access the variable with the value from the api request. I have rewrote the function that does the api request to use a completion handler. The mapView(mapView: GMSMapView!, didTapInfoWindowOfMarker marker: GMSMarker!) is a function from the google maps framework. Would I need to rewrite this as well to use take a completion handler ?
// variable
var website = ""
// code with api request
func getWebsite2(id: String, completion: (result: String) -> Void) {
var url = NSURL(string: "https://maps.googleapis.com/maps/api/place/details/json?placeid=\(id)&key=AIzaSyAWV1BUFv_vcedYroVrY7DWYuIxcHaqrv0")
self.dataTask = defaultSession.dataTaskWithURL(url!) {
data, respnse, error in
let json : AnyObject
do {
json = try NSJSONSerialization.JSONObjectWithData(data!, options: .AllowFragments)
var dictionArr = json["result"]
self.website = dictionArr!!["website"] as! String
print(self.website)
}
catch {
print(error)
}
}
self.dataTask?.resume()
}
// second function
func mapView(mapView: GMSMapView!, didTapInfoWindowOfMarker marker: GMSMarker!) {
let storeMarker = marker as! PlaceMarker
self.getWebsite2(storeMarker.id!) {
(result: String) in
print("inside did tap")
print(self.website)
// problem still here
// above two lines of code never run
}
self.performSegueWithIdentifier("toWebView", sender: nil)
}
// I initialize defaultSession and dataTask like this.
let defaultSession = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration())
var dataTask: NSURLSessionDataTask?

Answer 1

You are not invoking the completion handler passed into the getWebsite2 function. This (pseudo)code shows how to take the string received from the server and pass it to the closure invoked in didTapInfoWindowOfMarker.
func getWebsite2(id: String, completion: (result: String) -> Void) {
self.dataTask = defaultSession.dataTaskWithURL(url!) {
data, response, error in
// now on background thread
let someStringFromNetwork = data[0]
dispatch_async(dispatch_get_main_queue(),{
completion(someStringFromNetwork)
})
}
}

Answer 2

Firstly do not force unwrapping of the variables and always use do{} catch{} where it is required.
This small code block that show how you should handle try and if let conditions:
do {
let jsonObject = try NSJSONSerialization.JSONObjectWithData(data, options: []) as! [String:AnyObject]
if let dictionary = jsonObject["result"] as? [String: String] {
self.website = dictionary["website"]
} else {
print("Parse error")
}
} catch {
print("JSON error: \(error)")
}
Secondly defaultSession.dataTaskWithURL is asynchronous request that will set data only when he will finish.
In another worlds you try to print value when request is not finished.
For solving of youre problem you should use Completion Handlers.