Some of my http request has 'space' in URL, but it is not recognized by iPhone. I have to change 'space' to '%20' whenever there is a 'space' in the url. Now I have to send a message typed by the user to the server and it can have as many 'spaces' as the user like. It looks like I have to replace them all.(stringByReplacingOccurrencesOfString)
Convert 'space' to '%20' is the one I occasionally find. My question is which of the other characters in NSString cannot be straightly used by url on iPhone?
I think this is a better approach:
NSString* escapedUrl = [originalUrl
stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
If you want to understand how URL encoding works, take a look at this URL.
See RFC 2396 for the full gory details. The following characters must be escaped:
Control characters (ASCII 00-1F and 7F) Space < > # % "
The following characters are unwise to use without escaping because some gateways and other transport agents are known to sometimes modify such characters, or they are used as delimiters:
{ } | \ ^ [ ] `
来源：https://stackoverflow.com/questions/695911/question-about-character-of-nsstring-invalid-in-url-on-iphone