Codable (Encode & Decode) [Any] and [String: Any] Swift 5

CodableExtension.swift

// Original: https://gist.github.com/loudmouth/332e8d89d8de2c1eaf81875cfcd22e24
import Foundation

private struct JSONCodingKeys: CodingKey {
    var stringValue: String
    
    init(stringValue: String) {
        self.stringValue = stringValue
    }
    
    var intValue: Int?
    
    init?(intValue: Int) {
        self.init(stringValue: "\(intValue)")
        self.intValue = intValue
    }
}

extension KeyedDecodingContainer {
    func decode(_ type: [String: Any].Type, forKey key: K) throws -> [String: Any] {
        let container = try nestedContainer(keyedBy: JSONCodingKeys.self, forKey: key)
        return try container.decode(type)
    }
    
    func decode(_ type: [Any].Type, forKey key: K) throws -> [Any] {
        var container = try nestedUnkeyedContainer(forKey: key)
        return try container.decode(type)
    }
    
    func decode(_ type: [String: Any].Type) throws -> [String: Any] {
        var dictionary = [String: Any]()
        
        for key in allKeys {
            if let boolValue = try? decode(Bool.self, forKey: key) {
                dictionary[key.stringValue] = boolValue
            } else if let intValue = try? decode(Int.self, forKey: key) {
                dictionary[key.stringValue] = intValue
            } else if let stringValue = try? decode(String.self, forKey: key) {
                dictionary[key.stringValue] = stringValue
            } else if let doubleValue = try? decode(Double.self, forKey: key) {
                dictionary[key.stringValue] = doubleValue
            } else if let nestedDictionary = try? decode([String: Any].self, forKey: key) {
                dictionary[key.stringValue] = nestedDictionary
            } else if let nestedArray = try? decode([Any].self, forKey: key) {
                dictionary[key.stringValue] = nestedArray
            } else if let isValueNil = try? decodeNil(forKey: key), isValueNil == true {
                dictionary[key.stringValue] = nil
            } else {
                throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: codingPath + [key], debugDescription: "Unable to decode 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(Int.self) {
                array.append(value)
            } else if let value = try? decode(String.self) {
                array.append(value)
            } else if let value = try? decode(Double.self) {
                array.append(value)
            } else if let nestedDictionary = try? decode([String: Any].self) {
                array.append(nestedDictionary)
            } else if let nestedArray = try? decodeNestedArray([Any].self) {
                array.append(nestedArray)
            } else if let isValueNil = try? decodeNil(), isValueNil == true {
                array.append(Optional<Any>.none as Any)
            } else {
                throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: codingPath, debugDescription: "Unable to decode value"))
            }
        }
        return array
    }
    
    mutating func decode(_ type: [String: Any].Type) throws -> [String: Any] {
        let container = try nestedContainer(keyedBy: JSONCodingKeys.self)
        return try container.decode(type)
    }
    
    mutating func decodeNestedArray(_ type: [Any].Type) throws -> [Any] {
        var container = try nestedUnkeyedContainer()
        return try container.decode(type)
    }
}


extension KeyedEncodingContainerProtocol where Key == JSONCodingKeys {
    mutating func encode(_ value: [String: Any]) throws {
        for (key, value) in value {
            let key = JSONCodingKeys(stringValue: key)
            switch value {
            case let value as Bool:
                try encode(value, forKey: key)
            case let value as Int:
                try encode(value, forKey: key)
            case let value as String:
                try encode(value, forKey: key)
            case let value as Double:
                try encode(value, forKey: key)
            case let value as [String: Any]:
                try encode(value, forKey: key)
            case let value as [Any]:
                try encode(value, forKey: key)
            case Optional<Any>.none:
                try encodeNil(forKey: key)
            default:
                throw EncodingError.invalidValue(value, EncodingError.Context(codingPath: codingPath + [key], debugDescription: "Invalid JSON value"))
            }
        }
    }
}

extension KeyedEncodingContainerProtocol {
    mutating func encode(_ value: [String: Any]?, forKey key: Key) throws {
        guard let value = value else { return }
        
        var container = nestedContainer(keyedBy: JSONCodingKeys.self, forKey: key)
        try container.encode(value)
    }
    
    mutating func encode(_ value: [Any]?, forKey key: Key) throws {
        guard let value = value else { return }
        
        var container = nestedUnkeyedContainer(forKey: key)
        try container.encode(value)
    }
}

extension UnkeyedEncodingContainer {
    mutating func encode(_ value: [Any]) throws {
        for (index, value) in value.enumerated() {
            switch value {
            case let value as Bool:
                try encode(value)
            case let value as Int:
                try encode(value)
            case let value as String:
                try encode(value)
            case let value as Double:
                try encode(value)
            case let value as [String: Any]:
                try encode(value)
            case let value as [Any]:
                try encodeNestedArray(value)
            case Optional<Any>.none:
                try encodeNil()
            default:
                let keys = JSONCodingKeys(intValue: index).map({ [ $0 ] }) ?? []
                throw EncodingError.invalidValue(value, EncodingError.Context(codingPath: codingPath + keys, debugDescription: "Invalid JSON value"))
            }
        }
    }
    
    mutating func encode(_ value: [String: Any]) throws {
        var container = nestedContainer(keyedBy: JSONCodingKeys.self)
        try container.encode(value)
    }
    
    mutating func encodeNestedArray(_ value: [Any]) throws {
        var container = nestedUnkeyedContainer()
        try container.encode(value)
    }
}

Thanks for this 👍🏻

Just leaving a comment in case it helps anyone else.

I had a JSON that this was decoding, with double values with no decimal value (e.g. 25.0) - The ordering of the casting in this gist meant that it was cast as an Int successfully - and when accessing this value it was returning '25'

However, I was expecting doubles and in Swift, casting an Int (25) to a double, returns nil... the fix was to swap the ordering so that if it can be a double, it will be otherwise it will be an Int.