Learning the iOS 4 SDK for JavaScript Programmers

Capturing User-Entered Text

Like the two long-established text box elements in HTML (<text type="input"> and <textarea>), Cocoa Touch provides two types of text entry controls, UITextField and UITextView. The former is a one-line text box, while the latter allows for entry of multiple text lines in a scrollable area. In this section, you will add a UITextField to Workbench and learn how to obtain the text a user types into the text box.

Figure 9-8 shows how Workbench should look when you’ve finished this section. You will add both a UITextField and a UILabel so that when you finish entering text in the box, your code copies the text to the label and clears the text box in preparation for the next entry. To add just a little spice to the operation, the code converts the text to initial uppercase and applies one of three colors to the label’s text, depending on the length of the typed text.

Figure 9-8. Workbench app equipped for UITextField demonstration

The Code Portion

Begin by adding the necessary code to the WorkbenchViewController class files. In the header file, insert the notation that this class implements the UITextFieldDelegate. This will allow the text field control to send messages to the class when various conditions arise (although for this demo, you’re interested in acting only when editing ends with the press of the Return key on the keyboard). Next, add two instance variables ...