How to set focus to an iOS text field?

Make the textField the first responder; this will also popup the keyboard:

[self.textField becomeFirstResponder];

And just some more typical example code which may help someone,

in your storyboard, click on one of the text fields, and set the outlets-delegate to be the class in question. In that class, in the .h file make sure that you declare that it is a UITextFieldDelegate

@interface Login : UIViewController <UITextFieldDelegate>

Then in the .m file, you could have this for example…

-(BOOL)textFieldShouldReturn:(UITextField *)textField {
    if ( textField == self.loginEmail ) { [self.loginPassword becomeFirstResponder]; }
    if ( textField == self.loginPassword ) { [self yourLoginRoutine]; return YES; }
    return YES;
}

When a user clicks the “Next” button on the virtual keyboard – on the ’email’ field – it will correctly move you to the password field. When a user clicks the “Next” button on the virtual keyboard – on the ‘password’ field – it will correctly call your yourLoginRoutine.

(On the storyboard, on the attributes inspector, notice that you can select the text you want on the Return key … here “Next” would work nicely on the email field and “Done” would work nicely on the password field.)