First letter alphabet only and string is alphabet and numeric with limit in UITextField.

#define ALPHA @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz "

#define NUMERIC @"1234567890"

#define ALPHA_NUMERIC ALPHA NUMERIC

#define MAX_LENGTH 25

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

     

     NSCharacterSet *myCharSet = [[NSCharacterSet characterSetWithCharactersInString:@"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"] invertedSet];

     

     NSString* newStr = [itemname.text stringByTrimmingCharactersInSet:myCharSet];

     if ([newStr length] < 1)

     {

         unichar c =  [string characterAtIndex:0];;

         if ([myCharSet characterIsMember:c]) {

             return NO;

         }

     }else{

     

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

     

     NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString:ALPHA_NUMERIC] invertedSet];

     

     NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];

     

     while (newLength < MAX_LENGTH) {

         return [string isEqualToString:filtered];

     }

     return (newLength > MAX_LENGTH) ? NO : YES;

     }

    return YES;

    

}