Unable to limit characters to only alphanumeric inside UITextField in iOS

Question

In my iOS application, I have a UITextField that presently limits its character entry to 50 characters, and when it receives a single character, it enables a UIButton. What I am trying to do now is ensure that the user can only enter alphanumeric characters as well, but this is where I am having trouble. Here is the code that I have thus far:

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

BOOL canEdit=NO;
    NSCharacterSet *myCharSet = [NSCharacterSet alphanumericCharacterSet];
    NSUInteger newLength = [textField.text length] + [string length] - range.length;

    if (newLength > 0) {

        for (int i = 0; i < [string length]; i++)
        {
            unichar c = [string characterAtIndex:i];
            if (![myCharSet characterIsMember:c])
            {
                canEdit=NO;
                self.myButton.enabled = NO;
            }
            else
            {
                canEdit=YES;
                self.myButton.enabled = YES;
            }
        }

    }  else  self.myButton.enabled = NO;


    return (newLength > 50 && canEdit) ? NO : YES;
}

Originally, my code was just limiting the character entry to just 50 characters, and enabling my button looked like the following:

NSUInteger newLength = [textField.text length] + [string length] - range.length;

    if (newLength > 0) self.doneButton.enabled = YES;
    else self.doneButton.enabled = NO;

    return (newLength > 45) ? NO : YES;

The point I want to make is that I want to incorporate the limitation of alphanumeric characters within my existing code, and not replace it. This is the challenging part for me.

Hope this will help you..http://rajneesh071.blogspot.in/2012/12/how-to-restrict-user-to-enter-character.html — Rajneesh071, Feb 19 '14 at 05:27
You already [asked this, and got an answer](http://stackoverflow.com/questions/21864312/need-to-limit-characters-to-only-alphanumeric-in-existing-uitextfield-in-ios), then deleted your question. Don't repost. — jscs, Feb 19 '14 at 07:31

score 1 · Accepted Answer · answered Feb 19 '14 at 05:32

You will need to loop through and return NO to the method when the character is a non-alphanumeric one. So, the code that you have should be like:

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

    BOOL canEdit=NO;
    NSCharacterSet *myCharSet = [NSCharacterSet alphanumericCharacterSet];
    for (int i = 0; i < [string length]; i++) {
        unichar c = [string characterAtIndex:i];
        if (![myCharSet characterIsMember:c]) {
            return NO;
        }
    }
    NSUInteger newLength = [textField.text length] + [string length] - range.length;

    if (newLength > 0) {

        for (int i = 0; i < [string length]; i++)
        {
            unichar c = [string characterAtIndex:i];
            if (![myCharSet characterIsMember:c])
            {
                canEdit=NO;
                self.myButton.enabled = NO;
            }
            else
            {
                canEdit=YES;
                self.myButton.enabled = YES;
            }
        }

    }  else  self.myButton.enabled = NO;


    return (newLength > 50 && canEdit) ? NO : YES;
}

Unable to limit characters to only alphanumeric inside UITextField in iOS

1 Answers1