In this recipe, we will discuss the usage of the UITextField object and how we can display editable text within it.

In order to see how this can be achieved, we need to modify the ViewObjectsExample application that we created in the previous recipe. Perform the following steps to do so:

Our next step is to create the code functionality that will be responsible for displaying some text within our TextField control:

Our next step is to modify our ViewController.h interface file so that we can access the methods for our textbox. This can be achieved by performing the following simple steps:

Next, we need to modify our ViewController.m implementation file to include the method events for our textbox. This can be achieved by performing the following simple steps:

When the compilation completes, the iOS Simulator will appear and display the textbox with our populated sample text, as shown in the following screenshot:

In the following code snippet, we update the text property of the textField control and then set the returnKeyType property to dismiss the keyboard when the Done button is clicked and then set the delegate for the control to be our view controller:

-(void)populateTextBox {
  self.txtTextInput.text = @"This is some sample text";
  self.txtTextInput.returnKeyType = UIReturnKeyDone;
  self.txtTextInput.delegate = self;
}

Next, the UITextField class provides an object that displays editable text. In order for us to respond to the events of our textbox, we need to define a protocol class of UITextBoxDelegate that will act as the textbox's delegate, so that we can determine when text is being modified.

@interface ViewController : UIViewController <UITextFieldDelegate>
{
 IBOutlet UITextField *txtTextInput;
}
@property (weak, nonatomic) IBOutlet UITextField *txtTextInput;

In the following code snippet, we declare the textFieldShouldReturn: method of our TextField control. This method handles the dismissing of the keyboard when the Done button is pressed which is achieved by calling the resignFirstReponder method on the TextField control, causing the control to lose focus.

-(BOOL)textFieldShouldReturn:(UITextField *)textField {
        
    // Dismisses the keyboard when the "Done" button is clicked
    [textField resignFirstResponder];
    return YES;
}

Next, we declare the textFieldDidBeginEditing: and textFieldDidEndEditing: methods of our TextField control. These methods are responsible for determining when text is being updated within the text field and when the editing has been completed, which is achieved when the keyboard is dismissed.

-(void) textFieldDidBeginEditing:(UITextField *)textField
{
   lblInfo.text = @"TextField contents are being updated";
   [self.lblInfo setBackgroundColor:[UIColor redColor]];
}

-(void)textFieldDidEndEditing:(UITextField *)textField
{
 lblInfo.text = @"TextField contents have now been updated.";
 [self.lblInfo setBackgroundColor:[UIColor greenColor]];
}

A delegate in Objective-C is a certain type of object that conform to a specific protocol. This means that it is an object that wraps one or more methods (and/or other members) that act as event handlers.