https://github.com/krzyzanowskim/JSONCodable

JSONCodable.swift

import Foundation

public protocol JSONEncodable: Encodable {
  static var keyEncodingStrategy: JSONEncoder.KeyEncodingStrategy { get }
  static var dateEncodingStrategy: JSONEncoder.DateEncodingStrategy { get }
  static var dataEncodingStrategy: JSONEncoder.DataEncodingStrategy { get }
  static var nonConformingFloatEncodingStrategy: JSONEncoder.NonConformingFloatEncodingStrategy { get }

  func toJSON() throws -> Data
}

public extension JSONEncodable {
  static var keyEncodingStrategy: JSONEncoder.KeyEncodingStrategy { .convertToSnakeCase }
  static var dateEncodingStrategy: JSONEncoder.DateEncodingStrategy { .iso8601 }
  static var dataEncodingStrategy: JSONEncoder.DataEncodingStrategy { .base64 }
  static var nonConformingFloatEncodingStrategy: JSONEncoder.NonConformingFloatEncodingStrategy { .throw }
    
  func toJSON() throws -> Data {
    let encoder = JSONEncoder()
    encoder.keyEncodingStrategy = Self.keyEncodingStrategy
    encoder.dateEncodingStrategy = Self.dateEncodingStrategy
    encoder.dataEncodingStrategy = Self.dataEncodingStrategy
    encoder.nonConformingFloatEncodingStrategy = Self.nonConformingFloatEncodingStrategy
    return try encoder.encode(self)
  }
}

public protocol JSONDecodable: Decodable { 
  static var keyDecodingStrategy: JSONDecoder.KeyDecodingStrategy { get }
  static var dateDecodingStrategy: JSONDecoder.DateDecodingStrategy { get }
  static var dataDecodingStrategy: JSONDecoder.DataDecodingStrategy { get }
  static var nonConformingFloatDecodingStrategy: JSONDecoder.NonConformingFloatDecodingStrategy { get }

  static func from(json data: Data) throws -> Self
}

public extension JSONDecodable {
  static var keyDecodingStrategy: JSONDecoder.KeyDecodingStrategy { .convertFromSnakeCase }
  static var dateDecodingStrategy: JSONDecoder.DateDecodingStrategy { .iso8601 }
  static var dataDecodingStrategy: JSONDecoder.DataDecodingStrategy { .base64 }
  static var nonConformingFloatDecodingStrategy: JSONDecoder.NonConformingFloatDecodingStrategy { .throw } 
    
  static func from(json data: Data) throws -> Self {
    let decoder = JSONDecoder()
    decoder.keyDecodingStrategy = Self.keyDecodingStrategy
    decoder.dateDecodingStrategy = Self.dateDecodingStrategy
    decoder.dataDecodingStrategy = Self.dataDecodingStrategy
    decoder.nonConformingFloatDecodingStrategy = Self.nonConformingFloatDecodingStrategy
    return try decoder.decode(Self.self, from: data)
  }
}

public protocol JSONCodable: JSONEncodable & JSONDecodable {}

// Usage

struct Filter: JSONCodable {
  let id: String
}

let filter = Filter(id: "foo")
let encodedFilter = try filter.toJSON()
let jsonString = String(data: encodedFilter, encoding: .utf8)
let decodedFilter = try Filter.from(json: encodedFilter)