Change iOS tab view from alert - ios

Question

I have a tabbed application with 2 tab views. I want to change the view from the second tab to the first when the user presses "OK" on an alert view.
The following code snippet works when I use it on an -IBAction button pressed, but it doesn't do anything when I use it inside the alert code:
self.tabBarController.selectedViewController = [self.tabBarController.viewControllers objectAtIndex:0];
Why does it not work when used as below, in my SeondViewController.m in my
- (void)viewDidLoad {
[super viewDidLoad];?
UIAlertView *alert =[[UIAlertView alloc]
initWithTitle:#"Camera and Target coincident"
message:msg
delegate:nil
cancelButtonTitle:#"OK"
otherButtonTitles:nil];
[alert show];
self.tabBarController.selectedViewController = [self.tabBarController.viewControllers objectAtIndex:0];
I'm just learning this, so anything you can offer would be helpful.
When I use the following code:
if ([ theProjection Trans_Initialise] == 1) {
NSString * msg = nil;
UIAlertView *alertView =[[UIAlertView alloc] initWithTitle:#"Camera and Target coincident" message:msg delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil];
[alertView show];
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
if ([[alertView buttonTitleAtIndex:buttonIndex] isEqualToString:#"OK"]) {
self.tabBarController.selectedIndex = 0;
}
}
I get the error message on -(void) alertView "Invalid argument type void to unary expression" Am I doing something grammatical, or is it (quite possibly) something I just didn't understand?

Answer 1

First of all, you need a delegate call back from the alert view informing you about the button that was clicked.
Your alert view should be created like this :
UIAlertView *alert =[[UIAlertView alloc] initWithTitle:#"Camera and Target coincident" message:msg delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil];
Then in your m file implement the function :
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
if ([[alertView buttonTitleAtIndex:buttonIndex] isEqualToString:#"OK"]) {
self.tabBarController.selectedIndex = 0;
}
}