textfield animation for a specific character during input

I've got a textfield, which is using a numberpad for input, and I'd like to make it so that when the user types in a number, the textfield automatically inserts an ' (apostrophe) after the first digit, and any other numbers would follow the apostrophe. But to make this noticeable, I'd like to have th开发者_开发知识库e apostrophe 'pop up' with a change of color, before resting in the textfield. Much like the action of the keyboard letters when they're hit - they pop out for a second.

Seems to me there's several things to be done and I haven't found any help online with them:

1. Get notice after one digit is entered (more than one digit could be entered, but the animation would take place and the additional numbers would show up after the apostrophe).

2. Add the apostrophe into the textfield.

3. Animate the insertion of the apostrophe, while allowing the textfield to continually take in input.

Any direction to libraries or code or suggestions would be immensely appreciated. Thank you so much. I've a hunch I'm supposed to use coco2d but have no idea how to get started.

I figured out a work around that I'd thought I'd share in case anyone is interested. For monitoring input, you can use:

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string

which gets called when the user touches the keyboard, but before the character or number is processed and put to screen. The only problem is that on an empty text field, if the user hits backspace this method doesn't get called (even if not null). Basically because there's no change to an empty text field to process with an empty string.

You could also use: UITextFieldTextDidChangeNotification, but it gets called in the same way and doesn't offer any parameters to play with.

For 2: I ended up making labels for these and putting them over the text field where I wanted, and playing with their properties as needed. It was kind of messy so I actually split the text field into 2 and used the above method to jump in between. Seems to work mostly well, but dealing with the backspace issue is still unsolved (how to move back to the first text field when backspacing through text for example). Am considering overlaying a transparent button on that part of the keyboard. Seems messy though. I would appreciate any cleaner ideas that are out there.

So, didn't end up doing any animations, which would have been a much slicker. Hope this helps.