How to call an action when UISwitch changes state?

[yourSwitchObject addTarget:self action:@selector(setState:) forControlEvents:UIControlEventValueChanged]; 

This will call the below method when your switch state changes

- (void)setState:(id)sender 
{
    BOOL state = [sender isOn];
    NSString *rez = state == YES ? @"YES" : @"NO";
    NSLog(rez);
}