ios 自定義tabbar時 viewDidAppear不調用

自定義tabbar不點擊其他item時，默認controller的viewDidAppear的相關函數都不自動調用。在論壇逛了半天終於有人給出正確的解決辦法。這裏貼出來，以備不時之需。

-(void)viewWillAppear:(BOOL)animated
{
    [self.selectedViewController beginAppearanceTransition: YES animated: animated];
}
-(void) viewDidAppear:(BOOL)animated
{
    [self.selectedViewController endAppearanceTransition];
}
-(void) viewWillDisappear:(BOOL)animated
{
    [self.selectedViewController beginAppearanceTransition: NO animated: animated];
}
-(void) viewDidDisappear:(BOOL)animated
{
    [self.selectedViewController endAppearanceTransition];
}

在自定義的tabBarViewController中填上這塊代碼，就能完美解決上述問題。親測完美解決。