Codable+Convenience.swift

import Foundation

private class Nothing: Decodable { }

func decodeArray<T, U: Decodable>(_ container: KeyedDecodingContainer<T>, forKey key: T) throws -> [U] {
    var unkeyedContainer = try container.nestedUnkeyedContainer(forKey: key)
    var objects: [U] = []
    while !unkeyedContainer.isAtEnd {
        do {
            let object = try unkeyedContainer.decode(U.self)
            objects.append(object)
        } catch let error {
            log(error: "Failed to decode [\(U.self)]: \(error.localizedDescription)")
            
            // The unkeyedContainer does not progress to the next item
            // so we cheat by decoding any object.
            let _ = try? unkeyedContainer.decode([String: Nothing].self)
        }
    }
    return objects
}

func decodeArrayIfPresent<T, U: Decodable>(_ container: KeyedDecodingContainer<T>, forKey key: T) throws -> [U]? {
    
    guard container.contains(key) else {
        return nil
    }
    
    return try decodeArray(container, forKey: key)
}