Monday, September 13, 2010

Delegates Concept

delegate performs methods on behalf of another object. A Table View doesn't know what to do when you pick an item in the list. Instead, it has to ask the delegate object a question, specifically, didSelectRowAtIndexPath. The only information the tableview knows is which section and row the user tapped. So the table view gives this information to the delegate object by essentially saying that "Hey, the user tapped Row 4 in Section 0. Do something."

The delegate object finds the didSelectRowAtIndexPath method and executes the code inside.

There are lots of Delegate methods for many different objects. For instance, the Text Field object can't do anything on its own. Instead, it uses a delegate to perform actions. If you press the enter key on the on screen keyboard, the text field asks the delegate object to perform a specific method, textFieldShouldReturn. If the delegate you set for your text field does not have a textFieldShouldReturn method, the text field will not know what to do when you press the enter button.

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