Navigation bar and buttons considerations for iOS

Question

I have some questions regarding navigation bars and their usage in iOS apps, both from the point of view of UX and Apple´s submission and human interface guidelines:

1) Since the iOS Human Interface Guidelines state that

A navigation bar enables navigation through an information hierarchy and, optionally, management of screen contents.

and

You can use a navigation bar to enable navigation among different views, or provide controls that manage the items in a view.

should I assume that using a navigation bar in a view with no information hierarchy is not allowed, or just that it is not necessary? (For example, you have a tab bar and one of the tabs displays a player view or another single view, and to navigate to other view you have to tap another tab item).

2) It is also said in the Apple's document that

The navigation bar should contain no more than a view’s current title, the back button, and one control that manages the view’s contents

2.a) I've found Apple's apps "breaking" the rule of the back button at the left side (Calendar, iTunes), so... can I consider that, when they say "should" in their guidelines, it is just a recommendation but if I do things another way they won't reject my app?

2.b) I may need a button to be always visible in order to let users trigger its associated action at any moment, but I already have a tab bar at the bottom so I have to place such button within the nav bar (since I can't add a tool bar... or can I?). Is it required that such action always has "visibility" in the current view? (As, for instance, the button in the Twitter app that displays a "New Tweet" modal view whenever you want). For example, I'd want to set a button in the navigation bar for updating some data, and I'd want to have such button in all views in the app. But could it be that the data uploaded is not beign displayed in the current view but in another, or in another tab.

Thanks

Answer 1

If you need a back button to navigate around an iOS app, then you clearly need a navbar with a back button.

If however, you have a simple app that doesn't need any navigation, you can leave the back button out, or where it can be navigated entirely by using a tab bar, then a back becomes unnecessary.

Apple do this with many of their default iOS apps. The Facebook iOS app also leaves out the back button as it has a form of a tab bar with a slide out menu.

Guidelines are just that - guidelines. They provide a useful framework to work within, but you should always work to understand the intent of them and be ready to break the guidelines if it result in a better UX.