Annotation (Single Value Container)

Annotation.swift

struct Annotation: Decodable {
    let drawings: [Drawing]

    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        let string = try container.decode(String.self)
        guard let data = string.data(using: .utf8) else {
            let context = DecodingError.Context(codingPath: [], debugDescription: "Annotation data could not be serialized.")
            throw DecodingError.dataCorrupted(context)
        }
        self.drawings = try JSONDecoder().decode([Drawing].self, from: data)
    }
}