title: Check if a NSString is empty or only contains whitespace or tabs?
body: <p>I'm currently using <code>isEqualToString:@""</code> and it works fine when the textField does have nothing. However, it does not catch the case when the input has only white spaces or tabs. What should I do to make it smarter so that input such as <code>"    "</code> will not be allowed. </p>