Completion handler not working as expected in Swift

Question

I have these two functions below, using a completion handler. The questions is highlighted in comments of the 2nd function... why is the result part getting executed even before the asynchronous call in function checforViolationStatus() been completed.

func checkViolationStatus(usr: PFUser, completion: (result: Int32) -> Void) {
    var violations: Int32 = 0
    var query = PFQuery(className: PF_BLOCKEDUSERS_CLASS_NAME)
    query.whereKey(PF_BLOCKEDUSERS_USER, equalTo: usr)


    query.countObjectsInBackgroundWithBlock {
        (count: Int32, error: NSError?) -> Void in
        if error == nil {
            print("Result = \(count)")

            //The result here returned is 4, I can see it but always ZERO(0) gets printed in the main function. Unable to understand why.
            violations = count
        }
    }

    completion(result: violations)

}


    func goToMainMenu() {

    if PFUser.currentUser() != nil {

        self.mCould.checkViolationStatus(PFUser.currentUser()!) {
            (result: Int32) in

            //QUESTION: result is getting returned as ZERO even before the actual asynchronous call in the checkforViolation function has been completed - why????

            if result < 4 {
                //Go to Main Menu Screen
                print("result<=4 so calling segue")
                self.performSegueWithIdentifier("segueLoginVCToMainVC", sender: nil)
            } else {
                print("result >=4, so should not be doing anything")
            }

            print("Number of Violations Received Back: \(result)")

        }
    }


}

Downvoted because you make exactly the same mistake as in your previous question, without doing what I so carefully explained in my answer there. — matt, Oct 19 '15 at 02:11
yep, silly me. Yep you are right. wish you added it as an answer, would mark it. — user1406716, Oct 19 '15 at 02:13

score 1 · Answer 1 · answered Oct 19 '15 at 02:07

Try change your function to this,you should call completion in the countObjectsInBackgroundWithBlock,this method is async.

Or this function return before countObjectsInBackgroundWithBlock is finished

func checkViolationStatus(usr: PFUser, completion: (result: Int32) -> Void) {
var violations: Int32 = 0
var query = PFQuery(className: PF_BLOCKEDUSERS_CLASS_NAME)
query.whereKey(PF_BLOCKEDUSERS_USER, equalTo: usr)


query.countObjectsInBackgroundWithBlock {
    (count: Int32, error: NSError?) -> Void in
    if error == nil {
        print("Result = \(count)")

        //The result here returned is 4, I can see it but always ZERO(0) gets printed in the main function. Unable to understand why.
        violations = count
        completion(result: violations)

    }
}
}

Completion handler not working as expected in Swift

1 Answers1

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