Filtering characters entered into a UITextField

Question

I have a UITextField in my application. I\'d like to restrict the set of characters that can be can be entered into the field to a set that I have defined. I could filter th

Answer 1

How about this?

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

    NSString* regex = @"[^a-z]";
    return ([[string lowercaseString] rangeOfString: regex
                      options:NSRegularExpressionSearch].location == NSNotFound);
};

Note:

I am making all characters to lower case [string lowercaseString] so that you don't need to write in regex for captial/small letters.

Answer 2

This is what I use to restrict the user to uppercase A-Z. Adjust the regex variable according to taste:

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

    NSString* regex = @"[^A-Z]";
    return ([string rangeOfString: regex
                      options:NSRegularExpressionSearch].location == NSNotFound);
};

Answer 3

Look at the UITextViewDelegate method - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string.

It's exactly what you need.

Answer 4

I did as marcc suggested and it worked well. Sample implementation follows.

Note: Variable names were selected for brevity and do not reflect my coding standards:

    ...
    myCharSet = [NSCharacterSet characterSetWithCharactersInString:@"xyzXYZ"];
    ...
}

- (BOOL) textField:(UITextField*)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString*)textEntered {
    for (int i = 0; i < [textEntered length]; i++) {
        unichar c = [textEntered characterAtIndex:i];
        if (![myCharSet characterIsMember:c]) {
            return NO;
        }
    }
    return YES;
}

Answer 5

Here is one of the cleanest approaches to restricting characters entered in a UITextField. This approach allows the use of multiple predefined NSCharacterSets.

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

    NSMutableCharacterSet *allowedCharacters = [NSMutableCharacterSet alphanumericCharacterSet];
    [allowedCharacters formUnionWithCharacterSet:[NSCharacterSet whitespaceCharacterSet]];
    [allowedCharacters formUnionWithCharacterSet:[NSCharacterSet symbolCharacterSet]];

    if([string rangeOfCharacterFromSet:allowedCharacters.invertedSet].location == NSNotFound){

        return YES;

    }

    return NO;

}

Answer 6

You could loop and keep checking if the UITextField.text property has changed once the DidBeginEditing method gets called. If it has, check the text and remove an bad characters.