[英]Dynamic (But known as another key value) JSON Decoding with Swift Decodable
[英]Dynamic JSON Decoding Swift 4
我正在嘗試在Swift 4中解碼以下JSON:
{
"token":"RdJY3RuB4BuFdq8pL36w",
"permission":"accounts, users",
"timout_in":600,
"issuer": "Some Corp",
"display_name":"John Doe",
"device_id":"uuid824fd3c3-0f69-4ee1-979a-e8ab25558421"
}
問題是,JSON中的最后2個元素( display_name
和device_id
)可能存在也可能不存在,或者元素可能被命名為完全不同但仍然未知的東西,即"fred": "worker", "hours" : 8
所以我想要實現的是解碼已知的內容,即token
, permission
, timeout_in
和issuer
以及任何其他元素( display_name
, device_id
等)將它們放入字典中。
我的結構看起來像這樣:
struct AccessInfo : Decodable
{
let token: String
let permission: [String]
let timeout: Int
let issuer: String
let additionalData: [String: Any]
private enum CodingKeys: String, CodingKey
{
case token
case permission
case timeout = "timeout_in"
case issuer
}
public init(from decoder: Decoder) throws
{
let container = try decoder.container(keyedBy: CodingKeys.self)
token = container.decode(String.self, forKey: .token)
permission = try container.decodeIfPresent(String.self, forKey: .permission).components(separatedBy: ",")
timeout = try container.decode(Int.self, forKey: . timeout)
issuer = container.decode(String.self, forKey: .issuer)
// This is where I'm stuck, how do I add the remaining
// unknown JSON elements into additionalData?
}
}
// Calling code, breviated for clarity
let decoder = JSONDecoder()
let accessInfo = try decoder.decode(AccessInfo.self, from: data!)
能夠解碼JSON可能包含動態信息的已知結構的一部分,如果有人可以提供一些指導,我就在那里。
謝謝
受@matt評論的啟發,這是我已經完成的完整示例。 我擴展了KeyedDecodingContainer
來解碼未知密鑰並提供一個參數來過濾掉已知的CodingKeys
。
示例JSON
{
"token":"RdJY3RuB4BuFdq8pL36w",
"permission":"accounts, users",
"timout_in":600,
"issuer": "Some Corp",
"display_name":"John Doe",
"device_id":"uuid824fd3c3-0f69-4ee1-979a-e8ab25558421"
}
斯威夫特結構
struct AccessInfo : Decodable
{
let token: String
let permission: [String]
let timeout: Int
let issuer: String
let additionalData: [String: Any]
private enum CodingKeys: String, CodingKey
{
case token
case permission
case timeout = "timeout_in"
case issuer
}
public init(from decoder: Decoder) throws
{
let container = try decoder.container(keyedBy: CodingKeys.self)
token = container.decode(String.self, forKey: .token)
permission = try container.decode(String.self, forKey: .permission).components(separatedBy: ",")
timeout = try container.decode(Int.self, forKey: . timeout)
issuer = container.decode(String.self, forKey: .issuer)
// Additional data decoding
let container2 = try decoder.container(keyedBy: AdditionalDataCodingKeys.self)
self.additionalData = container2. decodeUnknownKeyValues(exclude: CodingKeys.self)
}
}
private struct AdditionalDataCodingKeys: CodingKey
{
var stringValue: String
init?(stringValue: String)
{
self.stringValue = stringValue
}
var intValue: Int?
init?(intValue: Int)
{
return nil
}
}
KeyedDecodingContainer擴展
extension KeyedDecodingContainer where Key == AdditionalDataCodingKeys
{
func decodeUnknownKeyValues<T: CodingKey>(exclude keyedBy: T.Type) -> [String: Any]
{
var data = [String: Any]()
for key in allKeys
{
if keyedBy.init(stringValue: key.stringValue) == nil
{
if let value = try? decode(String.self, forKey: key)
{
data[key.stringValue] = value
}
else if let value = try? decode(Bool.self, forKey: key)
{
data[key.stringValue] = value
}
else if let value = try? decode(Int.self, forKey: key)
{
data[key.stringValue] = value
}
else if let value = try? decode(Double.self, forKey: key)
{
data[key.stringValue] = value
}
else if let value = try? decode(Float.self, forKey: key)
{
data[key.stringValue] = value
}
else
{
NSLog("Key %@ type not supported", key.stringValue)
}
}
}
return data
}
}
調用代碼
let decoder = JSONDecoder()
let accessInfo = try decoder.decode(AccessInfo.self, from: data!)
print("Token: \(accessInfo.token)")
print("Permission: \(accessInfo.permission)")
print("Timeout: \(accessInfo.timeout)")
print("Issuer: \(accessInfo.issuer)")
print("Additional Data: \(accessInfo.additionalData)")
產量
Token: RdJY3RuB4BuFdq8pL36w
Permission: ["accounts", "users"]
Timeout: 600
Issuer: "Some Corp"
Additional Data: ["display_name":"John Doe", "device_id":"uuid824fd3c3-0f69-4ee1-979a-e8ab25558421"]
這個問題實際上是Swift 4 Decodable的復制品, 其密碼在解碼時間之前是未知的 。 一旦你理解了構建一個最底層的最小CodingKey采用者結構作為編碼密鑰的技巧,你就可以將它用於任何字典。
在這種情況下,您將使用鍵控容器的allKeys
來獲取未知的JSON字典鍵。
為了演示,我將僅限於JSON字典中完全未知的部分。 想象一下這個JSON:
let j = """
{
"display_name":"John Doe",
"device_id":"uuid824fd3c3-0f69-4ee1-979a-e8ab25558421"
}
"""
let jdata = j.data(using: .utf8)!
假設我們不知道該字典中的內容,除了它具有String鍵和String值之外。 所以我們想解析jdata
而不知道它的鍵是什么。
因此,我們有一個由一個字典屬性組成的結構:
struct S {
let stuff : [String:String]
}
現在的問題是如何將JSON解析為該結構 - 即,如何使該結構符合Decodable並處理該JSON。
這是如何做:
struct S : Decodable {
let stuff : [String:String]
private struct CK : CodingKey {
var stringValue: String
init?(stringValue: String) {
self.stringValue = stringValue
}
var intValue: Int?
init?(intValue: Int) {
return nil
}
}
init(from decoder: Decoder) throws {
let con = try! decoder.container(keyedBy: CK.self)
var d = [String:String]()
for key in con.allKeys {
let value = try! con.decode(String.self, forKey:key)
d[key.stringValue] = value
}
self.stuff = d
}
}
現在我們解析:
let s = try! JSONDecoder().decode(S.self, from: jdata)
我們得到一個S實例,其中的stuff
是這本字典:
["device_id": "uuid824fd3c3-0f69-4ee1-979a-e8ab25558421", "display_name": "John Doe"]
這就是我們想要的結果。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.