IOS: Unwind Segues

原文： http://www.intertech.com/Blog/iOS-Unwind-Segues/

In iOS 5, we were introduced to Storyboards and Segues.  While these features simplified the navigation process in our apps, we weren’t given a way to define a return to previous modal scenes via Interface Builder.

You may have noticed that in iOS 6, a green icon has been added to the control bar of each scene in the Storyboard.

This is a new, and surprisingly overlooked feature for iOS 6, which provides the missing “return” functionality.  It’s called an “unwind segue.”

The process is simple:

• Add a private method inside each View Controller you wish to “unwind” to (a common mistake is to add this code into the View Controller you wish to unwind from).
• This method includes one (and only one) parameter that’s a pointer to a UIStoryboardSegue, and a return type of IBAction .
• The name of this method can be whatever you’d like.  However, all of the unwind segues will be listed in one place,so it’s a good idea to pick a descriptive naming pattern, such as unwindToRootVC.
• There is no need to have anything in the body of this method.  The signature is what’s important.

   1: -(IBAction)unwindToRootVC:(UIStoryboardSegue *)segue

   2: {

   3:     // Nothing needed here.

   4: }

• Inside your Storyboard, hold the control key down while dragging from your button (or other control) to the green exit icon below.

• You will see a list of every unwind segue available here… that’s why coming up with a consistent and descriptive naming pattern is important.

That’s it!  You are now able to return to any previous scene simply by selecting the appropriate unwind segue.  Also, unlike following a ‘regular’ segue, this will use not create a new object for every request!

Read more: http://www.intertech.com/Blog/ios-unwind-segues/#ixzz39OhH56Aj 
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