如何在 Swift [45] 可解码协议中解码具有 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，它包含一个 metadata 属性，该属性可以包含客户对象中的任何 JSON 字典
struct Customer {让 ID:字符串让电子邮件:字符串让元数据:[字符串:任何]}<小时>
<代码>{对象":客户"，"id": "4yq6txdpfadhbaqnwp3","email": "john.doe@example.com",元数据":{"link_id": "链接 ID",购买计数":4}}metadata 属性可以是任意的 JSON 映射对象.
在我可以从 NSJSONDeserialization 的反序列化 JSON 转换属性之前，但使用新的 Swift 4 Decodable 协议，我仍然想不出办法做到这一点.
有谁知道如何在带有可解码协议的 Swift 4 中实现这一点?
a> 我发现，我为UnkeyedDecodingContainer 和KeyedDecodingContainer 写了一些扩展.您可以在此处找到我的要点链接.通过使用此代码，您现在可以使用熟悉的语法解码任何 Array 或 Dictionary:
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一个字典数组 [[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:
let items: [[String: Any]] = try container.decode(Array.self, forKey: .items) as![[字符串:任意]] 编辑 2:如果您只是想将整个文件转换为字典，最好坚持使用 JSONSerialization 中的 api，因为我还没有想出一种方法来扩展 JSONDecoder 本身以直接解码一本字典.
guard let json = try JSONSerialization.jsonObject(with: data, options: []) as?[字符串:任何]其他{//适当的错误处理返回}扩展
//灵感来自 https://gist.github.com/mbuchetics/c9bc6c22033014aa0c550d3b4324411a结构 JSONCodingKeys: CodingKey {var stringValue: 字符串初始化?(字符串值:字符串){self.stringValue = stringValue}var intValue: 整数?初始化?(整数值:整数){self.init(stringValue: "(intValue)")self.intValue = intValue}}扩展 KeyedDecodingContainer {func decode(_ type: Dictionary.Type, forKey key: K) throws ->字典<字符串，任意>{让容器 = 尝试 self.nestedContainer(keyedBy: JSONCodingKeys.self, forKey: key)返回 try container.decode(type)}func decodeIfPresent(_ type: Dictionary.Type, forKey key: K) throws ->字典<字符串，任意>?{守卫包含(键)其他{返回零}守卫尝试 decodeNil(forKey: key) == false else {返回零}返回尝试解码(类型，forKey:key)}func decode(_ type: Array.Type, forKey key: K) throws ->数组<任何>{var 容器 = 尝试 self.nestedUnkeyedContainer(forKey: key)返回 try container.decode(type)}func decodeIfPresent(_ type: Array.Type, forKey key: K) throws ->数组<任何>?{守卫包含(键)其他{返回零}守卫尝试 decodeNil(forKey: key) == false else {返回零}返回尝试解码(类型，forKey:key)}func decode(_ type: Dictionary.Type) 抛出 ->字典<字符串，任意>{var dictionary = Dictionary()对于所有键中的键 {如果让 boolValue = 尝试?解码(Bool.self，forKey:key){字典[key.stringValue] = boolValue} else if let stringValue = try?解码(String.self，forKey:key){字典[key.stringValue] = stringValue否则如果让 intValue = 尝试?解码(Int.self，forKey:key){字典[key.stringValue] = intValue否则如果让 doubleValue = 尝试?解码(双.self，forKey:key){字典[key.stringValue] = doubleValue否则如果让nestedDictionary = 试试?decode(Dictionary.self, forKey: key) {字典[key.stringValue] = 嵌套字典否则如果让nestedArray = 尝试?解码(数组.self，forKey:key){字典 [key.stringValue] = 嵌套数组}}返回字典}}扩展 UnkeyedDecodingContainer {mutating func decode(_ type: Array.Type) throws ->数组<任何>{var 数组:[Any] = []而 isAtEnd == false {//首先查看 JSON 数组中的当前值是否为 `null` 并防止嵌套数组的无限递归.如果尝试 decodeNil() {继续} else if let value = try?解码(Bool.self){数组.附加(值)} else if let value = try?解码(双.self){数组.附加(值)} else if let value = try?解码(字符串.self){数组.附加(值)否则如果让nestedDictionary = 试试?解码(字典<字符串，任何>.self){array.append(nestedDictionary)否则如果让nestedArray = 尝试?解码(数组<任何>.self){array.append(nestedArray)}}返回数组}mutating func decode(_ type: Dictionary.Type) 抛出 ->字典<字符串，任意>{让nestedContainer = 尝试self.nestedContainer(keyedBy: JSONCodingKeys.self)返回尝试 nestedContainer.decode(type)}} 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]
}
{
"object": "customer",
"id": "4yq6txdpfadhbaqnwp3",
"email": "john.doe@example.com",
"metadata": {
"link_id": "linked-id",
"buy_count": 4
}
}
The metadata property can be any arbitrary JSON map object.
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.
Do anyone know how to achieve this in Swift 4 with Decodable protocol?
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)
or
let array: [Any] = try container.decode([Any].self, forKey: key)
Edit: 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]]
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
}
The extensions
// 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)
}
}
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