swift4 codable decode different type in an array.

decode.swift

let str = """
{"jsonrpc": "2.0","result": [{"code": 1,"message": "error"},[{"gid": "123"}],{"code": 1,"message": "error2"},[{"gid": "124"}]]}
"""
let data = str.data(using: .utf8)!

struct JSONRPC: Decodable {
	
	enum DecodingError : Swift.Error, LocalizedError {
		case decodeMismatch(type: Any)
	}
	
	enum Result: Decodable {
		struct ArrayItem: Decodable {
			let code: Int
			let message: String
		}
		case array(ArrayItem)
		case dictionary([[String: String]])
		init(from decoder: Decoder) throws {
			let unkeyedContainer = try decoder.singleValueContainer()
			if let array = try? unkeyedContainer.decode(ArrayItem.self) {
				self = .array(array)
			} else if let dic = try? unkeyedContainer.decode([[String: String]].self) {
				self = .dictionary(dic)
			} else {
				throw DecodingError.decodeMismatch(type: decoder)
			}
		}
	}
	let version: String
	let results: [Result]
	private enum CodingKeys: String, CodingKey {
		case version = "jsonrpc"
		case results = "result"
	}
}
let decoder = JSONDecoder()
do {
	let array = try decoder.decode(JSONRPC.self, from: data)
	print(array.results)
} catch let error {
	print(error)
}