Understanding performSegueWithIdentifier

First, you have to have set up the segue in your storyboard and give it the appropriate identifier. (Click on the segue (left panel) and then click on Attributes (right panel).

You can then link this to buttons or selection of table rows from your storyboard, or you can call it in code using performSegueWithIdentifier:sender:.

After this, your view controller will be sent the prepareForSegue:sender: message. You override this method in your view controller subclass, and can configure the target view controller as follows:

TargetViewController *targetVC = (TargetViewController*)segue.destinationViewController;
targetVC.string1 = string1;

And so forth. The sender in this method will be the object that you use as the sender in the original method call.

Most segues are initiated automatically as the result of some user interaction. For instance, if you have a segue that is wired up from a button to a scene in a storyboard, when the button is tapped the segue will automatically initiate.

Occasionally, it makes sense to trigger a segue programmatically - e.g. you have a High Scores scene that is displayed when the user wins a round of a game. There's no way to express the concept of winning in the storyboard itself, so you can instead create a segue, assign an identifier to it, and invoke -performSegueWithIdentifier:sender: at runtime.

The other segue related method on UIViewController, -prepareForSegue:sender:, is the method you should override to perform any customization on the destination view controller.