To escape character use stringByAddingPercentEncodingWithAllowedCharacters:

NSString *URLEscapedString =

[string stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]];

The following are useful character sets:

URLFragmentAllowedCharacterSet? "#%<>[\]^`{|}

URLHostAllowedCharacterSet? ? ? "#%/<>?@\^`{|}

URLPasswordAllowedCharacterSet? "#%/:<>?@[\]^`{|}

URLPathAllowedCharacterSet? ? ? "#%;<>?[\]^`{|}

URLQueryAllowedCharacterSet? ? "#%<>[\]^`{|}

URLUserAllowedCharacterSet? ? ? "#%/:<>?@[\]^`