Async issue on getting values from the server - ios

Question

In my viewDidLoad I do:
// Get Profile Info
NSOperationQueue.mainQueue().addOperationWithBlock { () -> Void in
let getMyProfileURL = "\(self.property.host)\(self.property.getMyProfile)"
print(getMyProfileURL)
Alamofire.request(.POST, getMyProfileURL, parameters: self.property.profileParameteres, encoding: .JSON).responseJSON { response in
do {
let json = JSON(data: response.data!)
if json["user"].count > 0 {
self.profileDetails.append(ProfileDetailsModel(json: json["user"]))
}
}
}
print(self.profileDetails[0].firstName)
}
so, when I want to get the firstName from the array:
print(self.profileDetails[0].firstName)
my app crashes with the error:
fatal error: Array index out of range
My array is empty. I've used NSOperationQueue for it, but I still get empty array and crash. How can I fix this problem and access my filled array from anywhere in my controller, not only inside the Alamofire block?

Answer 1

The Request is Asynchronous, it will only fill the self.profileDetails array when it receive an answer, and execute the completionHandler block.
In your code, you call to execute the Asynchronous task, it will run in another thread, and the app goes back to the next operation and immediately try to access the self.profileDetails, with at the time may still be nil.
You must wait the completion handler block finish to fill the array, and then access the data.
The code of #Md.Muzahidul Islam , will work as you want.

Answer 2

Now it will work fine
NSOperationQueue.mainQueue().addOperationWithBlock { () -> Void in
let getMyProfileURL = "\(self.property.host)\(self.property.getMyProfile)"
print(getMyProfileURL)
Alamofire.request(.POST, getMyProfileURL, parameters: self.property.profileParameteres, encoding: .JSON).responseJSON { response in
do {
let json = JSON(data: response.data!)
if json["user"].count > 0 {
self.profileDetails.append(ProfileDetailsModel(json: json["user"]))
}
}
print(self.profileDetails[0].firstName)
}
}

Answer 3

I'd suggest refactoring your code to move this to a function outside of your viewDidLoad and then adding your own completion handler. Something like:
func getData(completion: () -> Void) {
NSOperationQueue.mainQueue().addOperationWithBlock { () -> Void in
let getMyProfileURL = "\(self.property.host)\(self.property.getMyProfile)"
print(getMyProfileURL)
Alamofire.request(.POST, getMyProfileURL, parameters: self.property.profileParameteres, encoding: .JSON).responseJSON { response in
do {
let json = JSON(data: response.data!)
if json["user"].count > 0 {
self.profileDetails.append(ProfileDetailsModel(json: json["user"]))
}
}
completion()
}
}
}
Then in viewDidLoad you can call it with its completion handler to access the data outside of the Alamofire block after it's finished, e.g.
getData() {
print(self.profileDetails[0].firstName)
}