swifturlencodenscharacterset

How to create a custom NSCharacterSet?

I’m using CharacterSet.urlQueryAllowed to add percent-encoding to a String.

Some characters are not encoded the way I expected (i.e. & and ? are not changed). That being said, I had the idea to build a custom CharacterSet, ideally based on an existing one.

What’s the best approach to do so?

Solution

  • The most typical way to create a new character set is using CharacterSet(charactersIn:), giving a String with all the characters of the set.

    Adding some characters to an existing set can be achieved using:

    let characterSet = NSMutableCharacterSet() //create an empty mutable set
characterSet.formUnionWithCharacterSet(NSCharacterSet.URLQueryAllowedCharacterSet())
characterSet.addCharactersInString("?&")

    or in Swift 3+ simply:

    var characterSet = CharacterSet.urlQueryAllowed
characterSet.insert(charactersIn: "?&")

    For URL encoding, also note Objective-C and Swift URL encoding