输入限制字母与数字

我们会经常用到限制字母与数字输入

#define kAlphaNum @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

#pragma mark -textFieldDelegate

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    // 限制只能输入 数字 和字母
    NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString:kAlphaNum] invertedSet];
    NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
    return [string isEqualToString:filtered];
    
}