iOs - unrecognized selector sent to instance on TextAction - ios

Question

i've some problem with this error :
ProjectName.ViewController textAction:]: unrecognized selector sent to instance 0x7fa60bc3840
The error appears when i try to create an alerte. Here is the code :
#IBAction func trySearch(sender: UIButton) {
self.api.getUser(self.textField.text!) { isResponse in
if (isResponse.count == 0) {
//Still crash HERE.
let alert = UIAlertController(title: "Error", message: "This username doesn't exist", preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(alert, animated: true, completion: nil)
}
else {
print("existing username")
}
}
If i comment all the alert code and replace it by a simple print it s works... I really don't understand why... Thank's !
getUser function:
func getUser(user: String, completion: ((isReponse: AnyObject) -> Void)) {
let request = NSMutableURLRequest(URL: NSURL(string: "https://********")!)
request.HTTPMethod = "GET"
request.setValue("Bearer \(self.loadToken())", forHTTPHeaderField: "Authorization")
Alamofire.request(request)
.responseJSON { response in
switch response.result {
case .Success(let JSON):
completion(isReponse: JSON)
case .Failure(let error):
print("Request failed with error: \(error)")
}
}
}
UPDATE : Same error when i click on "Done" of my TextField. + i add the getUser function.

Answer 1

You may be in the wrong thread, since you are presenting the alert within a block, try:
dispatch_async(dispatch_get_main_queue(), { _ in
let alert = UIAlertController(title: "Error", message: "This username doesn't exist", preferredStyle: UIAlertControllerStyle.Alert)
alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.Default, handler: nil))
self.presentViewController(alert, animated: true, completion: nil)
})

Answer 2

handler
A block to execute when the user selects the action. This block has no return value and takes the selected action object as its only parameter.
YOU don't assign action here.
Make like this:
UIAlertAction* ok = [UIAlertAction
actionWithTitle:#"OK"
style:UIAlertActionStyleDefault
handler:^(UIAlertAction * action)
{
//Do some thing here
[view dismissViewControllerAnimated:YES completion:nil];
}];
// add action to your alertController
[alert addAction:ok];
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIAlertAction_Class/#//apple_ref/occ/clm/UIAlertAction/actionWithTitle:style:handler: