如何在 Swift [45] 可解码协议中解码 JSON 字典类型的属性 [英] How to decode a property with type of JSON dictionary in Swift [45] decodable protocol
问题描述
假设我有 Customer 数据类型，其中包含一个 metadata 属性，该属性可以包含客户对象中的任何 JSON 字典
Let's say I have Customer data type which contains a metadata property that can contains any JSON dictionary in the customer object
struct Customer {
let id: String
let email: String
let metadata: [String: Any]
}
<小时>
{
"object": "customer",
"id": "4yq6txdpfadhbaqnwp3",
"email": "john.doe@example.com",
"metadata": {
"link_id": "linked-id",
"buy_count": 4
}
}
metadata 属性可以是任意 JSON 地图对象.
The metadata property can be any arbitrary JSON map object.
在我可以从 NSJSONDeserialization 的反序列化 JSON 中转换属性但使用新的 Swift 4 Decodable 协议之前，我仍然想不出办法做到这一点.
Before I can cast the property from a deserialized JSON from NSJSONDeserialization but with the new Swift 4 Decodable protocol, I still can't think of a way to do that.
有人知道如何在 Swift 4 中使用 Decodable 协议实现这一点吗?
Do anyone know how to achieve this in Swift 4 with Decodable protocol?
推荐答案
灵感来自 这个要点 我发现，我为 UnkeyedDecodingContainer 和 KeyedDecodingContainer 编写了一些扩展.您可以在此处找到我的要点的链接.通过使用此代码，您现在可以使用熟悉的语法解码任何 Array<Any> 或 Dictionary<String, Any>:
With some inspiration from this gist I found, I wrote some extensions for UnkeyedDecodingContainer and KeyedDecodingContainer. You can find a link to my gist here. By using this code you can now decode any Array<Any> or Dictionary<String, Any> with the familiar syntax:
let dictionary: [String: Any] = try container.decode([String: Any].self, forKey: key)
或
let array: [Any] = try container.decode([Any].self, forKey: key)
我发现有一个警告是解码字典数组[[String: Any]] 所需的语法如下.您可能希望抛出错误而不是强制转换:
there is one caveat I have found which is decoding an array of dictionaries [[String: Any]] The required syntax is as follows. You'll likely want to throw an error instead of force casting:
let items: [[String: Any]] = try container.decode(Array<Any>.self, forKey: .items) as! [[String: Any]]
编辑 2: 如果您只是想将整个文件转换为字典，则最好坚持使用 JSONSerialization 中的 api，因为我还没有找到扩展 JSONDecoder 本身以直接解码的方法一本字典.
EDIT 2: If you simply want to convert an entire file to a dictionary, you are better off sticking with api from JSONSerialization as I have not figured out a way to extend JSONDecoder itself to directly decode a dictionary.
guard let json = try JSONSerialization.jsonObject(with: data, options: []) as? [String: Any] else {
// appropriate error handling
return
}
扩展
// Inspired by https://gist.github.com/mbuchetics/c9bc6c22033014aa0c550d3b4324411a
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: Dictionary<String, Any>.Type, forKey key: K) throws -> Dictionary<String, Any> {
let container = try self.nestedContainer(keyedBy: JSONCodingKeys.self, forKey: key)
return try container.decode(type)
}
func decodeIfPresent(_ type: Dictionary<String, Any>.Type, forKey key: K) throws -> Dictionary<String, Any>? {
guard contains(key) else {
return nil
}
guard try decodeNil(forKey: key) == false else {
return nil
}
return try decode(type, forKey: key)
}
func decode(_ type: Array<Any>.Type, forKey key: K) throws -> Array<Any> {
var container = try self.nestedUnkeyedContainer(forKey: key)
return try container.decode(type)
}
func decodeIfPresent(_ type: Array<Any>.Type, forKey key: K) throws -> Array<Any>? {
guard contains(key) else {
return nil
}
guard try decodeNil(forKey: key) == false else {
return nil
}
return try decode(type, forKey: key)
}
func decode(_ type: Dictionary<String, Any>.Type) throws -> Dictionary<String, Any> {
var dictionary = Dictionary<String, Any>()
for key in allKeys {
if let boolValue = try? decode(Bool.self, forKey: key) {
dictionary[key.stringValue] = boolValue
} else if let stringValue = try? decode(String.self, forKey: key) {
dictionary[key.stringValue] = stringValue
} else if let intValue = try? decode(Int.self, forKey: key) {
dictionary[key.stringValue] = intValue
} else if let doubleValue = try? decode(Double.self, forKey: key) {
dictionary[key.stringValue] = doubleValue
} else if let nestedDictionary = try? decode(Dictionary<String, Any>.self, forKey: key) {
dictionary[key.stringValue] = nestedDictionary
} else if let nestedArray = try? decode(Array<Any>.self, forKey: key) {
dictionary[key.stringValue] = nestedArray
}
}
return dictionary
}
}
extension UnkeyedDecodingContainer {
mutating func decode(_ type: Array<Any>.Type) throws -> Array<Any> {
var array: [Any] = []
while isAtEnd == false {
// See if the current value in the JSON array is `null` first and prevent infite recursion with nested arrays.
if try decodeNil() {
continue
} else if let value = try? decode(Bool.self) {
array.append(value)
} else if let value = try? decode(Double.self) {
array.append(value)
} else if let value = try? decode(String.self) {
array.append(value)
} else if let nestedDictionary = try? decode(Dictionary<String, Any>.self) {
array.append(nestedDictionary)
} else if let nestedArray = try? decode(Array<Any>.self) {
array.append(nestedArray)
}
}
return array
}
mutating func decode(_ type: Dictionary<String, Any>.Type) throws -> Dictionary<String, Any> {
let nestedContainer = try self.nestedContainer(keyedBy: JSONCodingKeys.self)
return try nestedContainer.decode(type)
}
}
这篇关于如何在 Swift [45] 可解码协议中解码 JSON 字典类型的属性的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
