Clash Royale CLAN TAG

confused about optional chaining and nil coalescing operator in Swift

I'm having difficulty understanding the exercise below:

Assume the following structs and enum are defined.

enum Genre: String {
case country, blues, folk
}

struct Artist {
let name: String
var primaryGenre: Genre?
}

struct Song {
let title: String
let released: Int
var artist: Artist?
}

Using the enums and structures, implement the getArtistGenre() function. Given a Song as input, return the raw value of the artist's primary genre. If either the artist is nil or the primaryGenre is nil, then return an empty string. You must use optional chaining and the nil coalescing operator (??).

enum Genre: String {
case country, blues, folk
}

struct Artist {
let name: String
var primaryGenre: Genre?
}

struct Song {
let title: String
let released: Int
var artist: Artist?
}

func getArtistGenre(song: Song) -> String {

}

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