UITextField, automatically move to next after 1 character

Question

Scenario: I have 4 UITextFields that only accept 1 character. Easy.

Problem: After I enter the 1 character, I want the next TextField to become active automatically with

Answer 1

I arrived at a solution by modifying some code I found here: http://www.thepensiveprogrammer.com/2010/03/customizing-uitextfield-formatting-for.html

First set the your view controller to be the delegate of the textfields.

Then do something like this:

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{   
    BOOL shouldProcess = NO; //default to reject
    BOOL shouldMoveToNextField = NO; //default to remaining on the current field

    int insertStringLength = [string length];
    if(insertStringLength == 0){ //backspace
        shouldProcess = YES; //Process if the backspace character was pressed
    }
    else {
        if([[textField text] length] == 0) {
            shouldProcess = YES; //Process if there is only 1 character right now
        }
    }

    //here we deal with the UITextField on our own
    if(shouldProcess){
        //grab a mutable copy of what's currently in the UITextField
        NSMutableString* mstring = [[textField text] mutableCopy];
        if([mstring length] == 0){
            //nothing in the field yet so append the replacement string
            [mstring appendString:string];

            shouldMoveToNextField = YES;
        }
        else{
            //adding a char or deleting?
            if(insertStringLength > 0){
                [mstring insertString:string atIndex:range.location];
            }
            else {
                //delete case - the length of replacement string is zero for a delete
                [mstring deleteCharactersInRange:range];
            }
        }

        //set the text now
        [textField setText:mstring];

        [mstring release];

        if (shouldMoveToNextField) {
            //
            //MOVE TO NEXT INPUT FIELD HERE
            //
        }
    }

    //always return no since we are manually changing the text field
    return NO;
}