How to compose multi-character emoji from raw hex

I'm getting JSON like this from the server:

{
    "unicode":"1f468-1f468-1f467-1f467"
}

and I'm supposed to translate it into its composite character for display and/or copying to the pasteboard: ‍‍‍

The solution so far comes from this SO question:

let u = json["unicode"] as? String
let dashless = u.characters.split{$0 == "-"}.map(String.init)
let charArray = dashless.map { char -> Character in
    let code = Int(strtoul(char, nil, 16))
    return Character(UnicodeScalar(code))
}
let unicode = String(charArray)
UIPasteboard.generalPasteboard().string = unicode

This works great for single-character emoji definitions.

E.g., I can run the code above with this JSON…

{
    "unicode":"1f4a9"
}

…and paste the expected result: . But when I do with the mmgg family emoji listed earlier, I get the following in iOS, minus the spaces: ‍ ‍ ‍ . They just don't seem to want to combine when pasted into a text field.

Is this an iOS bug, or am I doing something wrong?