Question

I want to validate length and restrict Numeric, alphanumeric, and alpha characters only in iOS, can anyone help me out to achieve this.

Answer 1

Found best Way to tackle this thing. Works like a champ 🙂

inside .m file

//#define CHARACTERS @" ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

//#define CHARACTERS_NUMBERS  [CHARACTERS stringByAppendingString:@"1234567890"]
///// Inside shouldChangeCharactersInRange 

///////////>>>>>>>>>>>>>>>>>> 

if(textField== txtFldAlpha)
    {

        //Alpha only

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

        NSCharacterSet *unacceptedInput =
        [[NSCharacterSet characterSetWithCharactersInString:CHARACTERS] invertedSet];

        // Create array of strings from incoming string using the unacceptable
        // characters as the trigger of where to split the string.
        // If array has more than one entry, there was at least one unacceptable character
        if ([[string componentsSeparatedByCharactersInSet:unacceptedInput] count] > 1)
            return NO;
        else 
            return YES&&(newLength < 26);
        return YES;
    }

///////////<<<<<<<<<<<<<<<<<<

///////////>>>>>>>>>>>>>>>>>>

if(textField==txtFldNumeric)
    {
        //Num only

        NSUInteger newLength = [textField.text length] + [string length] - range.length;
        NSCharacterSet *nonNumberSet = [[NSCharacterSet decimalDigitCharacterSet] invertedSet];

        if ([[string componentsSeparatedByCharactersInSet:nonNumberSet] count] > 1)
            return NO;
        else 
            return YES&&(newLength < 6);
        return YES;

    }

///////////<<<<<<<<<<<<<<<<<<

///////////>>>>>>>>>>>>>>>>>>

if(textField==txtFieldNumAlphaSpecial)
    {
        //Num,Alpha,Special field

        NSUInteger newLength = [textField.text length] + [string length] - range.length;
        return (newLength > 50) ? NO : YES;
    }    
///////////<<<<<<<<<<<<<<<<<<