Swift Conversion UTF16 to UTF8 and back - swift

Question

I'm building an app in Swift an I'm using Backendless as my backend. Turns out their database is UTF8 and thus I can't save emojis without converting the String first.
I can't seem to find the right way to make this conversion to UTF8. I tried this:
let encoding = processedText.stringByAddingPercentEscapesUsingEncoding(NSUTF8StringEncoding)
But after this operation the emojis look like this:
%F0%9F%99%84%F0%9F%98%80%F0%9F%98%92%F0%9F%98%89%F0%9F%98%B6%F0%9F%98%B6%F0%9F%98%80%F0%9F%99%81
And I tried this:
class func stringToUTF8String (string: String) -> String? {
let encodedData = string.dataUsingEncoding(NSUTF8StringEncoding)!
let attributedOptions = [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType]
do{
let attributedString = try NSAttributedString(data: encodedData, options: attributedOptions, documentAttributes: nil)
return attributedString.string
}catch _ {
}
return nil
}
And the emojis look like this:
🤔🤔👅ðŸ™ðŸ˜‚😭😎😉😅😉
Does anyone have any suggestions? Thanks

Answer 1

First, to create a String from NSData with utf8 encoding you use
String(data: theData, encoding: NSUTF8StringEncoding)
Second, swift String's already are unicode compliant. You do not have to convert them as they already do that. You can access different encodings with their respective properties, e.g. String.utf8, String.utf16, and so on.
Third, to have NSAttributedString properly utf8 encode your string from data you have to add NSCharacterEncodingDocumentAttribute key to the attributedOptions dictionary with the value NSUTF8StringEncoding.
Final notes, I don't know if that's a partial method, but attributed string shouldn't be used just to encode a string.
Here is NSAttributedString encoding the data in some format returning gibberish.
Here is NSAttributedString encoding data as utf8 and returning correct text.
Here is encoding a string as utf8 string.
I know it's an image, but I wanted the results to show. If these don't work, the database may be stripping bits. Which sucks, also have no idea what to do then, and you probably shouldn't use that database if you want unicode support.