init.swift

init(from decoder: Decoder) throws {
    let baseContainer = try decoder.container(keyedBy: BaseContent.CodingKeys.self)
    let type = try baseContainer.decode(BaseContent.ContentType.self, forKey: .type)

    let container = try decoder.singleValueContainer()

    switch type {
    case .header:
        self = .header(try container.decode(Header.self))
    case .paragraph:
        self = .paragraph(try container.decode(Paragraph.self))
    case .footer:
        self = .footer(try container.decode(Footer.self))
    }
}