March 2013
Intermediate to advanced
1000 pages
34h 51m
English
Content preview from Programming iOS 6, 3rd EditionBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Navigation Controllers
A navigation bar (UINavigationBar, see also Chapter 25) is a horizontal bar displaying, at its simplest, a center title and a right button. When the user taps the right button, the navigation bar animates, sliding its interface out to the left and replacing it with a new interface that enters from the right, displaying a back button at the left side, and a new center title — and possibly a new right button. Thus the user can now either go further forward (to the right), tapping the right button to proceed to yet another center title, or else go back (to the left), tapping the back button to return to the first center title and the first right button.
There’s a computer science name for the architecture I’m describing — a stack. Conceptually, a navigation bar represents a stack. Under the hood, a navigation bar really is a stack. A navigation bar holds an internal stack of navigation items (UINavigationItem). It starts out with one navigation item (the root or bottom item); you can then push another navigation item onto the stack, and from there you can either pop that navigation item to remove it from the stack or push yet another navigation item onto the stack.
At any moment, therefore, some navigation item is the top item on the stack, the most recently pushed item still present on the stack (the topItem). Furthermore, unless the top item is also the root item (because it is the only item in the stack), some navigation item is the back item (the backItem
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.