Why sometimes viewDidLoad is called first and sometimes it's called latter?

Question

-(void) tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController
{
    [[NSNotificationCenter defaultCenter] postNotificationName:ListOrMapAddReloadButton object:self]; //Add nearby buttons
}

In one UIViewController here is the sequence

1. viewDidload get called
2. [[NSNotificationCenter defaultCenter] postNotificationName:ListOrMapAddReloadButton object:self];

And because the notification set up is called at viewDidLoad, I kind of need viewDidLoad to be called first before `

1. -(void) tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController

`

How could I achieve that?

[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(addReloadButton) name:ListOrMapAddReloadButton object:nil];
[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(addNearbyButton) name:ListOrMapAddNearbyButton object:nil];

Answer 1

Put your notifications in ViewWillAppear ()