Decode [String:Any] property by Decodable in Swift

DictionaryDecoding.swift

struct AnyCodingKeys: CodingKey {
    var stringValue: String
    var intValue: Int?

    init?(stringValue: String) { self.stringValue = stringValue }
    
    init?(intValue: Int) {
        self.stringValue = String(intValue)
        self.intValue = intValue
    }
}

extension KeyedDecodingContainer {
    func decode(_ type: [Any].Type, forKey key: K) throws -> [Any] {
        var container = try self.nestedUnkeyedContainer(forKey: key)
        return try container.decode(type)
    }
    
    func decodeIfPresent(_ type: [Any].Type, forKey key: K) throws -> [Any]? {
        guard contains(key) else { return .none }
        return try decode(type, forKey: key)
    }
    
    func decode(_ type: [String:Any].Type, forKey key: K) throws -> [String:Any] {
        let container = try nestedContainer(keyedBy: AnyCodingKeys.self, forKey: key)
        return try container.decode(type)
    }
    
    func decodeIfPresent(_ type: [String:Any].Type, forKey key: K) throws -> [String:Any]? {
        guard contains(key) else { return .none }
        return try decode(type, forKey: key)
    }
    
    func decode(_ type: [String:Any].Type) throws -> [String:Any] {
        var dictionary = [String:Any]()
        
        allKeys.forEach { key in
            if let value = try? decode(Bool.self, forKey: key) {
                dictionary[key.stringValue] = value
            } else if let value = try? decode(String.self, forKey: key) {
                dictionary[key.stringValue] = value
            } else if let value = try? decode(Int64.self, forKey: key) {
                dictionary[key.stringValue] = value
            } else if let value = try? decode(Double.self, forKey: key) {
                dictionary[key.stringValue] = value
            } else if let value = try? decode([String:Any].self, forKey: key) {
                dictionary[key.stringValue] = value
            } else if let value = try? decode([Any].self, forKey: key) {
                dictionary[key.stringValue] = value
            }
        }
        
        return dictionary
    }
}

extension UnkeyedDecodingContainer {
    mutating func decode(_ type: [Any].Type) throws -> [Any] {
        var array = [Any]()
        
        while isAtEnd == false {
            if let value = try? decode(Bool.self) {
                array.append(value)
            } else if let value = try? decode(String.self) {
                array.append(value)
            } else if let value = try? decode(Int64.self) {
                array.append(value)
            } else if let value = try? decode(Double.self) {
                array.append(value)
            } else if let value = try? decode([String:Any].self) {
                array.append(value)
            } else if let value = try? decode([Any].self) {
                array.append(value)
            }
        }
        
        return array
    }
    
    mutating func decode(_ type: [String:Any].Type) throws -> [String:Any] {
        let nestedContainer = try self.nestedContainer(keyedBy: AnyCodingKeys.self)
        return try nestedContainer.decode(type)
    }
}

struct A: Decodable {
    let title: String
    let payload: Payload
    
    struct Payload: Decodable {
        let items: [String:Any]
        public init(from decoder: Decoder) throws {
            let container = try decoder.container(keyedBy: AnyCodingKeys.self)
            items = try container.decode([String:Any].self)
        }
    }
}

let jsonString = """
{
    "title":"abc",
    "payload": {
        "int": 1,
        "string": "2",
        "array": {
            "bool": true,
            "double": 2.34
        }
    }
}
"""
let jsonData = jsonString.data(using: .utf8)!
let a = try! JSONDecoder().decode(A.self, from: jsonData)
print(a)