Auto-formatting phone number UITextField on the iPhone

In this post, we'll use our PhoneNumberFormatter to implement an auto-formatting phone number text field in an attempt to mimic the behavior of iPhone's native apps, like Phone and Contacts.

So, let's call the text field in question myTextField. We start by calling addTarget on the text field to make it call the autoFormatTextField method in our view controller whenever it gets updated, either by the user or some other piece of code. If your view is ready, you should declare the handler as an IBAction and bind through IB. The method would then update the contents of the text fields to the formatted string returned by the formatter. If we do it that way, we'll also need to use a semaphore to prevent the method from being called endlessly.

The implementation outline would be:

// declarations

UITextField *myTextField;

int myTextFieldSemaphore;

PhoneNumberFormatter *myPhoneNumberFormatter;

NSString *myLocale; //@"us"



// init semaphore

myTextFieldSemaphore = 0;



// bind events programatically, skip when using IB.

[myTextField addTarget:self

                action:@selector(autoFormatTextField:)

      forControlEvents:UIControlEventValueChanged

];



// handle events

- (void)autoFormatTextField:(id)sender {

 if(myTextFieldSemaphore) return;

 myTextFieldSemaphore = 1;

 myTextField.text = [phoneNumberFormatter format:myTextField.text withLocale:myLocale];

 myTextFieldSemaphore = 0;

}

Update: As pointed out in the comments, for newer SDKs you may need to bind to UIControlEventEditingChanged. Thanks for your feedback!

//bind events

[myTextField addTarget:self

                action:@selector(autoFormatTextField:)

      forControlEvents:UIControlEventEditingChanged

];