Json Values Append Array but ViewDidLoad it seem Empty - ios

Question

I am working in iOS and when I take JSON datas , I print it with no error in the function and append it a String array ( I did it correctly )
But if I want to reach to String array later the json Function it seem empty array . For testing I printed the array in a Button Action then it worked for me but I want to use in String Datas in other Function when Json Function ends.
The Codes:
func getAllDataFromURL()
{
var i : Int = 0;
var urlDatas : [String] = allJsonDatas.getAllTours();
for(i = 0 ; i < allJsonDatas.getAllTours().count ; i += 1)
{
Alamofire.request(.GET, urlDatas[i]).responseJSON
{(response) -> Void in
if let arrivedData = response.result.value
{
print("********")
print(arrivedData["generalTourDistrict"] as! String);
print(arrivedData["otherTourDistrict"] as! String);
print(arrivedData["photoURLS"] as! [String]);
print(arrivedData["subTourDistrict"] as! String);
print(arrivedData["tourCalendar"] as! String);
print(arrivedData["tourDistrict"] as! String);
print(arrivedData["tourName"] as! String);
self.tryingSomething.appendContentsOf(arrivedData["photoURLS"] as! [String]);
print("********\n")
}
}
}
}
And viewDidLoad is
override func viewDidLoad() {
super.viewDidLoad()
Alamofire.Request.addAcceptableImageContentTypes(acceptableContentTypes);
self.getAllDataFromURL();
self.printTheJsonDatas();
}
For Example , in getAllDataFromURL() function I can print it correctly.
This is the result for url data from the json:
["https://acenta.dominant.com.tr//dominant/webout/R12/php/product/img.php?path=L2QvMS9jcmkvc295a3VsL3VydW4vMDAvMjIvMTIvaW1hZ2UvL3VfMDAyMjEyLjAwMDAxLmpwZWc=&rx=650&ry=400", "https://acenta.dominant.com.tr//dominant/webout/R12/php/product/img.php?path=L2QvMS9jcmkvc295a3VsL3VydW4vMDAvMjIvMTIvaW1hZ2UvL3VfMDAyMjEyLjAwMDA2LmpwZWc=&rx=650&ry=400"]
But printTheJsonDatas() prints an empty array like -> [ ]
func printTheJsonDatas()
{
print(tryingSomething)
//tryingSomething : [String]
}
Surprisingly , when I put printTheJsonDatas() into buttonClickedAction, then it worked as I said before.
I think the problem is about threads but I can not say anything clearly .

Answer 1

You are calling both your web service request and print functions consecutive like they are both syncronous but they are not. When you make a web servic request with Alamofire it works asyncronous. So you can not expect it to finish in a certain time in future. What you should do is call your print function in .response block of the Alamofire request:
func getAllDataFromURL()
{
var i : Int = 0;
var urlDatas : [String] = allJsonDatas.getAllTours();
for(i = 0 ; i < allJsonDatas.getAllTours().count ; i += 1)
{
Alamofire.request(.GET, urlDatas[i]).responseJSON
{(response) -> Void in
if let arrivedData = response.result.value
{
self.tryingSomething.appendContentsOf(arrivedData["photoURLS"] as! [String]);
self.printTheJsonDatas();
}
}
}
}
An other problem with your code is it is making multiple web service call. Even if you call your print function in .response block it probably wont work as you think. It will print multiple times with different sizes.

Answer 2

getAllDataFromURL() runs asynchronously with a completion block (known as a closure in swift, or callback on other languages). The order of events is:
getAllDataFromURL()
printTheJsonDatas()
Alamofire.request()
(wait for AF response)
self.tryingSomething.appendContentsOf(...)
If you want the print function to work correctly, you'll need to call it inside the completion block of the AF request, e.g.:
func getAllDataFromURL()
{
var i : Int = 0;
var urlDatas : [String] = allJsonDatas.getAllTours();
for(i = 0 ; i < allJsonDatas.getAllTours().count ; i += 1)
{
Alamofire.request(.GET, urlDatas[i]).responseJSON
{(response) -> Void in
if let arrivedData = response.result.value
{
self.tryingSomething.appendContentsOf(arrivedData["photoURLS"] as! [String]);
//
self.printTheJsonDatas();
// ^
}
}
}
}
You could also rewrite getAllDataFromURL() with a closure to be asynchronous (the more appropriate way to write this, I'd say):
func getAllDataFromURL(completion: (result: Array) -> Void) {
...
var returnArray = []
// ^ here this is a local variable, doesn't need to be global anymore
returnArray.appendContentsOf(arrivedData["photoURLS"] as! [String]);
completion(returnArray)
}