unrecognized selector sent to instance + crash when pressing UIBarButtonItem - ios

Question

I get the NSException "unrecognized selector sent to instance" and then my app crashes whenever the btnReload UIBarButtonItem is pressed. I included the code for what the method does for the action, however the crash/exception occurs whether or not the testChangingViewController method has code.
All of the following code is in my UIViewController class.
- (void)loadView //use loadView because not a storyboard based GUI.
{
[super loadView];
UIBarButtonItem *btnReload =[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh target:self action:#selector(testChangingViewController:)];
self.navigationController.topViewController.navigationItem.leftBarButtonItem = btnReload;
btnReload.enabled=TRUE;
//self.view = [[UIView alloc] initWithFrame:[[UIScr een mainScreen] bounds]];
[self.view setBackgroundColor:[UIColor whiteColor]];
[self setTitle:#"Navigation"]; //navigation bar title tied to the view controller it is managing.
UIImageView *friendsIcon = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"change_user-512"]];
[friendsIcon setFrame:CGRectMake(60, 130, 70, 70)];
[self.view addSubview:friendsIcon];
UIImageView *statusIcon = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"talk-512"]];
[statusIcon setFrame:CGRectMake(180,130, 70, 70)];
[self.view addSubview:statusIcon];
UIView *square = [[UIView alloc] initWithFrame:CGRectMake(250, 250, 50, 50)];
[square setBackgroundColor:[UIColor orangeColor]];
[self.view addSubview:square];
// Do any additional setup after loading the view.
}
-(void)testChangingViewController
{
UITableViewController *newViewController = [[UITableViewController alloc] initWithStyle:UITableViewStylePlain];
[self.navigationController pushViewController:newViewController animated:YES];
}

Answer 1

You assign the UIBarButtonItem the #selector(testChangingViewController:) (colon at end, one parameter) but you define the method testChangingViewController (no colon, no params). The selector it is looking for that takes a parameter is not present, hence your error. These target selectors always tend to have one parameter, the "sender", that is, the UIControl that generated the event.