如何在 Swift 4 可编码协议中使用 JSON 字典类型对属性进行编码

Question

嗯，我的问题很简单。我想做与此答案相同的操作，但要进行编码： How to decode a property with type of JSON dictionary in Swift 4 decodable protocol

该解决方案适用于解码，但我还需要编码 Dictionary<String, Any>

我不知道如何为KeyedEncodingContainer 和其他扩展编写扩展，以及编写什么方法。

Answer 1

您可以通过修改该问题答案中的可解码代码 sn-p 来做到这一点

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)
    }
}

这是一个代码sn-p

但是，这段代码 sn-p 在 Swift 4.1 中会失败，应该在 2018 年上半年发布。