ASIHttpRequest parses URL with spaces

When ASIHttpRequest parses URL with spaces ， the App error will occur.

For Example . When you input something liking this :
http://myWebApp?clientName=Phone Li

The most troublesome issue will come to find you.

Using "stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding" ,when you get a bad url.

The sample of my code is：

NSString *newUrl = [oldUrl stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];