EnumDecodable.swift

protocol EnumDecodable: RawRepresentable, Decodable {
	static func defaultDecoderValue() throws -> Self
}

enum EnumDecodableError: Swift.Error {
	case noValue
}

extension EnumDecodable {
	static func defaultDecoderValue() throws -> Self {
		throw EnumDecodableError.noValue
	}
}

extension EnumDecodable where RawValue: Decodable {
	init(from decoder: Decoder) throws {
		let value = try decoder.singleValueContainer().decode(RawValue.self)
		self = try Self(rawValue: value) ?? Self.defaultDecoderValue()
	}
}

// May be used as

enum MediaType: String, Decodable {
	static func defaultDecoderValue() throws -> MediaType {
		return .other
	}

	case audio = "AUDIO"
	case multipleChoice = "MULTIPLE_CHOICES"
	case other
}

// or

enum MediaType: String, Decodable {
	case audio = "AUDIO"
	case multipleChoice = "MULTIPLE_CHOICES"
}

// Note that since `RawRepresentable` declares a `encode(coder:)` by default, any `EnumDecodable` can be also specified
// `Codable` with no changes to the code.