Type-safe Encodable Dictionary - useful for building quick dynamic Encodable packets

EncodableDictionary.swift

public struct EncodableDictionary {
    typealias EncodingFunction = (inout KeyedEncodingContainer<AnyCodingKey>) throws -> Void
    
    // MARK: - Private Properties
    private var data: [String: Any] = [:]
    private var encodings: [String: EncodingFunction] = [:]
    
    // MARK: - Lifecycle
    public init() { }
    
    // MARK: - Public Functions
    public subscript<T: Encodable>(key: String) -> T? {
        get { return data[key] as? T }
        set { updateEncoding(key: key, newValue: newValue) }
    }
    
    // MARK: - Private Functions
    private mutating func updateEncoding<T: Encodable>(key: String, newValue: T?) {
        data[key] = newValue
        encodings[key] = newValue.map { value in
            return { try $0.encode(value, forKey: AnyCodingKey(key)) }
        }
    }
}

extension EncodableDictionary: Encodable {
    public func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: AnyCodingKey.self)
        for (_, encoding) in encodings {
            try encoding(&container)
        }
    }
}

Usage.swift

var dict = EncodableDictionary()
dict["foo"] = 42
dict["bar"] = true

let json = String(data: try JSONEncoder().encode(dict), encoding: .utf8)!)
print(json) // {"bar":true,"foo":42}

AnyCodingKey: https://gist.github.com/IanKeen/3d226854c8c59a17e151a0022b71f6bb