iOS - 限制UITextField仅输入数字

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
   return [self validateNumber:string];
}

- (BOOL)validateNumber:(NSString*)number {
   BOOL res = YES;
   NSCharacterSet* tmpSet = [NSCharacterSet characterSetWithCharactersInString:@"0123456789"];
   int i = 0;
   while (i < number.length) {
       NSString * string = [number substringWithRange:NSMakeRange(i, 1)];
       NSRange range = [string rangeOfCharacterFromSet:tmpSet];
       if (range.length == 0) {
           res = NO;
           break;
       }
       i++;
   }
   return res;
}