如何在Swift 4可编码协议中使用JSON字典类型编码属性

Question

Well, my question is simple. I want to do the same as this answer but for encode: How to decode a property with type of JSON dictionary in Swift 4 decodable protocol

That solution works fine with decode, but I also need encode a Dictionary<String, Any>

I can't realize how to write the extension for KeyedEncodingContainer and the other extensions, and what methods to write.

Answer 1

You can do that by adapting the Decodable code snippet from that question's answer

extension KeyedEncodingContainerProtocol where Key == JSONCodingKeys {
    mutating func encodeJSONDictionary(_ value: Dictionary<String, Any>) throws {
        try value.forEach({ (key, value) in
            let key = JSONCodingKeys(key: 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 Dictionary<String, Any>:
                try encode(value, forKey: key)
            case let value as Array<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: Dictionary<String, Any>, forKey key: Key) throws {
        var container = self.nestedContainer(keyedBy: JSONCodingKeys.self, forKey: key)
        try container.encodeJSONDictionary(value)
    }

    mutating func encodeIfPresent(_ value: Dictionary<String, Any>?, forKey key: Key) throws {
        if let value = value {
            try encode(value, forKey: key)
        }
    }

    mutating func encode(_ value: Array<Any>, forKey key: Key) throws {
        var container = self.nestedUnkeyedContainer(forKey: key)
        try container.encodeJSONArray(value)
    }

    mutating func encodeIfPresent(_ value: Array<Any>?, forKey key: Key) throws {
        if let value = value {
            try encode(value, forKey: key)
        }
    }
}

extension UnkeyedEncodingContainer {
    mutating func encodeJSONArray(_ value: Array<Any>) throws {
        try value.enumerated().forEach({ (index, value) in
            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 Dictionary<String, Any>:
                try encode(value)
            case let value as Array<Any>:
                try encode(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 encodeJSONDictionary(_ value: Dictionary<String, Any>) throws {
        var nestedContainer = self.nestedContainer(keyedBy: JSONCodingKeys.self)
        try nestedContainer.encodeJSONDictionary(value)
    }
}

Here's a code snippet for that

However, this code snippet will fail in Swift 4.1 which should be released within the first half of 2018.