Is there a way to combine switch and contains?

Question

Let's assume that I have three sets containing extensions:

let photos: Set = ["jpg", "png", "tiff"]
let videos: Set = ["mp4", "mov", "mkv"]
let audios: Set = ["mp3", "wav", "wma"]

and a simple enum as:

enum FileType {
    case photo, video, audio, unknown
}

Now what I want to do is to implement a function that returns FileType option based on what is the passed string to it and which set contains it:

func getType(of file: String) -> FileType {
    if photos.contains(file) { return .photo }
    if videos.contains(file) { return .video }
    if audios.contains(file) { return .audio }

    return .unknown
}

It should work as expected, but I wonder if there is an approach to transform the if statement to one switch case (even if it would change the logic a bit), especially when working with enums the switch statement(s) is a better choice to avoid errors.

If it is unachievable by using switch statement, I would also appreciate any elegant alternative(s).

Answer 1

I think your whole problem is the fact that you are trying to maintain 3 independent sets for every type instead of connecting them directly to a given file type:

enum FileType: String {
    case photo, video, audio, unknown
}

let extensions: [FileType: Set<String>] = [
    .photo: ["jpg", "png", "tiff"],
    .video: ["mp4", "mov", "mkv"],
    .audio: ["mp3", "wav", "wma"]
]

func getType(of file: String) -> FileType {
    return extensions.first { $0.value.contains(file) }?.key ?? .unknown
}