How to hide the keyboard when I press return key in a UITextField?

First make your file delegate for UITextField

@interface MYLoginViewController () <UITextFieldDelegate>

@end

Then add this method to your code.

- (BOOL)textFieldShouldReturn:(UITextField *)textField {        
    [textField resignFirstResponder];
    return YES;
}

Also add self.textField.delegate = self;

In viewDidLoad declare:

[yourTextField setDelegate:self];

Then, include the override of the delegate method:

-(BOOL)textFieldShouldReturn:(UITextField *)textField
{
    [textField resignFirstResponder];
    return YES;
}

Try this in Swift,

Step 1: Set delegate as self to your textField

textField.delegate = self

Step 2: Add this UITextFieldDelegate below your class declaration,

extension YourClassName: UITextFieldDelegate {
    func textFieldShouldReturn(textField: UITextField) -> Bool {
         textField.resignFirstResponder()
        return true
    }
}