Storyboards make it easy to pass data from one scene to another via the prepareForSegue:sender: method of the UIViewController class. This method is called when the first scene (the source) is about to transition to the next scene (the destination). The source view controller can implement prepareForSegue:sender: to perform setup tasks, such as passing information to the destination view controller about what it should display in its table view. Listing 3-1 shows one implementation of this method.

Storyboards利用func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!)将数据从一个界面传输到另外一个界面。这个函数在源界面切换到目标界面的时候会调用。所以在源View Controller中可以重载func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!)这个方法，在该方法内完成将数据传送到目的View Controller。下面就是这个函数一般的实现方式。

(Objective-C)
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([[segue identifier] isEqualToString:@"ShowDetails"]) { MyDetailViewController *detailViewController = [segue destinationViewController];
    NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];
    detailViewController.data = [self.dataController
objectInListAtIndex:indexPath.row];
} }


(Swift)

func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) {

        if(segue.identifier == "ShowDetails"){

            var detailViewController:MyDetailViewController ! = segue.destinationViewController as MyDetailViewController

　　　　　　　var index = tableView.indexPathForSelectedRow()

            detailViewController.data = dataController[index!.row]

        }

}

A segue represents a one-way transition from a source scene to a destination scene. One of the consequences of this design is that you can use a segue to pass data to a destination, but you can’t use a segue to send data from a destination to its source. To solve this problem, you create a delegate protocol that declares methods that the destination view controller calls when it needs to pass back some data.

Segue是条从源界面到目标界面的一条路。你可以通过Segue将数据从源界面->目标界面。