viewWillAppear method doesn't work - swift

Question

import UIKit
class ViewController: UIViewController {
#IBOutlet weak var family_name: UITextField!
#IBOutlet weak var given_name: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
override func viewWillAppear(animated: Bool) {
family_name.center.x -= view.bounds.width
given_name.center.x -= view.bounds.width
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
viewWillAppear has no effect. When I run my app both text fields shouldn't be visible, but they are. I attached a photo with constraints; I think this can be the problem!

Answer 1

You are using autolayout, so frame change will not apply. your constraints will overwrite frame values after viewWillAppear:
Create IBOutlet for either right constraint or width constraint of your textFields.
Check below sample image to create IBOutlet of constraint.
In above image I have create outlet of height constraint.
To send textField outside of the view, suppose you have created right constraint.
//suppose initial value of right constraint is 20
constraintTextView1Right.constant = 20 + self.view.bounds.width;
self.view.layoutIfNeeded();//forcefully apply constraint with new values
After this, at some point in button click or in other event or after some delay, you can change value of constraintTextView1Right to 20,
constraintTextView1Right.constant = 20
self.view.layoutIfNeeded();//forcefully apply constraint with new values
your textFiled will come in the screen.
To animate the same you can write below code.
constraintTextView1Right.constant = 20
UIView.animateWithDuration(0.3) { () -> Void in
self.view.layoutIfNeeded();//forcefully apply constraint with new values
}