Objective C nsstring encoded as URL special character processing

Looking for the online tutorials are using code similar to the following, Xcode hints that this corefoundation is not managed by arc, so the tradeoff is to add __bridge.

NSString *encodedvalue = (__bridge NSString *) cfurlcreatestringbyaddingpercentescapes (nil,

(cfstringref) unencodedstring, Nil,

(cfstringref) @ "!*" ();: @&=+$,/?%#[] ", kCFStringEncodingUTF8);

But there's a really good solution.

NSString *encodedvalue=[unencodedstring Stringbyaddingpercentencodingwithallowedcharacters:[nscharacterset Alphanumericcharacterset]];

Use the NSString built-in API.

Objective C nsstring encoded as URL special character processing