How should i handle Alamofire response in shouldPerformSegueWithIdentifier? - swift

Question

I am trying to learn Swift and what i am trying to do is to create simple login page. Whenever user click on login button, i make a request to my web service in shouldPerformSegueWithIdentifier in order to check if username and password is correct. I dont want to use IBAction (like touchupinside etc). After parsing response that comes from web service, i check if there is any error comes from web service response (like user name is not valid). If there is any error I would like to prevent segue by returning false. But i cant return false inside of Alamofire. So how should i handle it? Here is my code :
override func shouldPerformSegueWithIdentifier(identifier: String?, sender: AnyObject?) -> Bool {
if identifier == "segueLoginToMainPage" {
//...
//Checking if text fields are filled or not
else {
let callURL : String = CONFIG.BASE_URL + "user/login"
let parameters = [HTTPParamNames.FIELD_USER_NAME : self.txtUserName.text,
HTTPParamNames.FIELD_PASSWORD : self.txtPassword.text]
Alamofire.request(.POST, callURL, parameters: parameters)
.responseJSON { (_,_,JSON,_) in
var returnedData = JSON as NSDictionary
if returnedData["status"] as String == "error" {
//thats what i want to do
return false
}
}
}
}
return true
}
But i cant do return false because it is async. I have found some questions like this in stackoverflow but answers are not what exactly i am looking for. Thanks!

Answer 1

You simply should not try to use asynchronous method within shouldPerformSegueWithIdentifier. Instead you should:
Remove segue from login button, itself.
Add segue between the view controllers, themselves. Specifically, control-drag from the originating scene's view controller icon (in Xcode 6+, this icon is in the bar above the scene, in earlier versions of Xcode, this icon is in the bar below the scene) to the destination scene.
Give this new segue a "storyboard identifier".
Hook up login button to an IBAction function.
In that IBAction function, perform your asynchronous network request, and if the login was successful, then programmatically performSegueWithIdentifier, supplying the storyboard identifier that you specified in step 3.

Answer 2

I think that not using IBAction is a good solution in this case but anyway there is a workaround how to achieve your goal. For this workaround you need to declare a variable typed boolean to check wether user is ready to login. Your shouldPerformSegueWithIdentifier method should always return value of that variable but after you make a request. Finally after your asynchronous request finishes call the prepareForSegue method
var readyForLogin = false
override func shouldPerformSegueWithIdentifier(identifier: String?, sender: AnyObject?) -> Bool {
if identifier == "segueLoginToMainPage" {
//...
//Checking if text fields are filled or not
else {
if(!readyForLogin){
let callURL : String = CONFIG.BASE_URL + "user/login"
let parameters = [HTTPParamNames.FIELD_USER_NAME : self.txtUserName.text,
HTTPParamNames.FIELD_PASSWORD : self.txtPassword.text]
Alamofire.request(.POST, callURL, parameters: parameters)
.responseJSON { (_,_,JSON,_) in
var returnedData = JSON as NSDictionary
if returnedData["status"] as String != "error" {
//thats what i want to do
self.readyForLogin = true
self.performSegueWithIdentifier("segueLoginToMainPage", sender: self)
}
}
}}
}
return readyForLogin
}