viewWillAppear in viewcontrollers of a tabbar

In my tab-bar I have four viewcontrollers, and what happens in one can affect the view of the other, so I may need to reload some elements in th开发者_JS百科e viewcontroller when it becomes visible. Normally I'd fix that by implementing viewWillAppear, but when I switch between the tabs, viewWillAppear does not seem to get called. How can I fix that, or what should I do instead?

Update: as a PS I should add that this is a tabbarcontroller in a navigationcontroller hierarchy

Cheers

Nik

You may use the tabbar controller delegate works like a charm

-(void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController
{
    [viewController viewWillAppear:YES];

}

Please see my answer here

iPhone viewWillAppear not firing

And in case you find this question because you would like to update something in the UITabBarController itself, not the UIViewControllers of a UITabBarController, like the OP's question. For example, hiding or displaying a custom UITabBarButton. In Swift 3.0 overriding setNeedsStatusBarAppearanceUpdate of my UITabBarController class worked for me.

override func setNeedsStatusBarAppearanceUpdate() {

}

viewWillAppear should only be used when the view appears, and not for updating it.

Use setNeedsDisplay on the viewController's view instead.