Global array only returns 0 - ios

Question

I have instantiated a global array called array and try append the values from dictionary to the array. I have successfully copied the values from the dictionary to the array but it seems to only locally. I am not sure where I have done wrong. Please help me figure it out. Here's the code :
class StudentTableViewController: UITableViewController {
var dict = Dictionary<String, String> ()
var array = [Dictionary<String, String>] ()
// Student
override func viewDidLoad() {
super.viewDidLoad()
queryData()
}
func queryData ()-> (Int, [Dictionary<String, String>]) {
var userQuery = PFUser.query()
//var arr = []
var count : Int
count = 0
userQuery?.whereKey("Type", equalTo:"student")
userQuery?.findObjectsInBackgroundWithBlock({ (objects: [AnyObject]?, error: NSError?) -> Void in
for object in objects! {
self.dict["firstName"] = object["firstName"] as! NSString as String
self.dict["lastName"] = object["lastName"] as! NSString as String
self.dict["contact"] = object["contact"] as! NSString as String
self.array.append(self.dict)
}
println(self.array)
count = self.array.count
})
return(self.array.count, self.array)
// returns 0
// return empty array
}
Here, self.array.count return 0 but I want to return the count of the dictionary members and the self.array only return empty array where I want it to return the dictionary.
I have been stuck on this for a while, I am not sure why it doesn't want to be global
Thanks

Answer 1

findObjectsInBackgroundWithBlock is asynchronous, so when your method returns, the block hasn't even run yet. Instead, you need to call something in your block with the results. Here is an example of how to do this by passing a completion block.
override func viewDidLoad() {
super.viewDidLoad()
queryData {
// update view
}
}
func queryData(completionHandler: () -> Void) {
var userQuery = PFUser.query()
var count : Int
count = 0
userQuery?.whereKey("Type", equalTo:"student")
userQuery?.findObjectsInBackgroundWithBlock({ (objects: [AnyObject]?, error: NSError?) -> Void in
for object in objects! {
self.dict["firstName"] = object["firstName"] as! NSString as String
self.dict["lastName"] = object["lastName"] as! NSString as String
self.dict["contact"] = object["contact"] as! NSString as String
self.array.append(self.dict)
}
println(self.array)
count = self.array.count
dispatch_async(dispatch_get_main_queue) {
completion()
}
})
return(self.array.count, self.array)
}