我有解码JSON的问题。我正在尝试解码我的JSON
let temp = try JSONDecoder().decode([LastTemperatureResponse].self, from: data)。
我的Codable结构如下：
struct LastTemperatureResponseElement: Codable {
let measurement: Measurement
}
struct Measurement: Codable {
let ts: String
let sensors: [VportSensor]
}
struct VportSensor: TemperatureSensor, Codable {
var lastUpdate: String!
let address, description: String
let status: String
let temperature: Double
}
好吧，如果我正在尝试解码我的JSON，我会收到错误信息，其中很清楚
keyNotFound(CodingKeys(stringValue: "status", intValue: nil), Swift.DecodingError.Context(codingPath: [_JSONKey(stringValue: "Index 0", intValue: 0), CodingKeys(stringValue: "measurement", intValue: nil), CodingKeys(stringValue: "sensors", intValue: nil), _JSONKey(stringValue: "Index 0", intValue: 0)], debugDescription: "No value associated with key CodingKeys(stringValue: \"status\", intValue: nil) (\"status\").", underlyingError: nil))
但请看看我的JSON
[
{
"type": "temperatures",
"ts": "2017-11-08T16:43:59.558Z",
"source": "thermo-king",
"unit": {
"number": "1226000743"
},
"measurement": {
"ts": "2017-11-08T16:43:18.000Z",
"sensors": [
{
"address": "t1",
"description": "LFTest1",
"setpoints": [
{
"address": "s1",
"name": "LFSTest1"
}
]
},
{
"address": "t2",
"description": "LFTest2",
"setpoints": [
{
"address": "s2",
"name": "LFSTest2"
}
]
},
{
"address": "t3",
"description": "LFTest3",
"setpoints": [
{
"address": "s3",
"name": "LFSTest3"
}
]
},
{
"address": "t4",
"description": "LFTest4"
},
{
"address": "t5",
"description": "LFTest5"
},
{
"address": "t6",
"description": "LFTest6"
}
],
"sensor": {
"address": "t1",
"name": "LFTest1"
},
"setpoints": [
{
"address": "s1",
"name": "LFSTest1"
}
]
}
},
{
"type": "temperatures",
"ts": "2018-06-07T07:05:38.962Z",
"source": "1-wire",
"unit": {
"number": "1226000743"
},
"measurement": {
"ts": "2018-06-07T07:05:31.000Z",
"sensors": [
{
"address": "2839A5B104000004",
"description": "1-wire #1",
"status": "ok",
"temperature": 24.8
},
{
"address": "28EFBAB104000061",
"description": "1-wire #3",
"status": "ok",
"temperature": 24.5
},
{
"address": "2845F6B504000034",
"description": "1-wire #2",
"status": "ok",
"temperature": 24.5
}
],
"sensor": {
"address": "2839A5B104000004",
"name": "1-wire #1",
"status": "ok"
},
"temperature": 24.8
}
},
{
"type": "temperatures",
"ts": "2018-06-07T07:11:50.030Z",
"source": "vport",
"unit": {
"number": "1226000743"
},
"measurement": {
"ts": "2018-06-07T07:11:47.000Z",
"sensors": [
{
"address": "1036040010",
"description": "Vport 1-wire",
"status": "high",
"temperature": 26
}
],
"sensor": {
"address": "1036040010",
"name": "Vport 1-wire",
"status": "high"
},
"temperature": 26
}
}
]
因此，我可以猜测由于数据的第一部分而给出错误，但是应该省略它还是用其余的数据生成数据？
在追踪你的问题之后，我认为有几个问题，首先：
您没有声明可选项：
基于附加的json，似乎有一些并不总是存在的属性，例如：
status => VportSensor。temperature => Measurement。temperature => VportSensor。temperature => setpoints。您需要确保声明任何可能未作为可选项收到的属性。
此外，可编码结构的实施：
实现的结构似乎不是json响应结构的典型结构，请确保声明您的可编码结构与接收的json结构相匹配。
注意：
lastUpdate和description不用于VportSensor。TemperatureSensor ...小费：
当涉及到使用日期（例如ts）时，你应该直接将它声明为Date而不是String，然后设置方便的dateDecodingStrategy。在你的情况下，它应该是一个自定义的，你可以找到如何在this answer中做到这一点。
基于以上描述，有完整的实现：
struct Main: Codable {
let type: String
let ts: Date
let source: String
let unit: Unit
let measurement: Measurement
}
struct Unit: Codable {
var number: String
}
struct Measurement: Codable {
let ts: String
let sensors: [VportSensor]
let sensor: VportSensor
let temperature: Double?
}
struct LastTemperatureResponseElement: Codable {
let measurement: Measurement
}
struct VportSensor: Codable {
//let lastUpdate: String!
//let description: String
let address: String
let name: String?
let status: String?
let temperature: Double?
let setpoints: [Setpoint]?
}
struct Setpoint: Codable {
let address: String
let name: String
}
// this part from the mentioned answer for creating custom `dateDecodingStrategy`:
enum DateError: String, Error {
case invalidDate
}
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .custom({ (decoder) -> Date in
let container = try decoder.singleValueContainer()
let dateStr = try container.decode(String.self)
let formatter = DateFormatter()
formatter.calendar = Calendar(identifier: .iso8601)
formatter.locale = Locale(identifier: "en_US_POSIX")
formatter.timeZone = TimeZone(secondsFromGMT: 0)
formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSXXXXX"
if let date = formatter.date(from: dateStr) {
return date
}
formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssXXXXX"
if let date = formatter.date(from: dateStr) {
return date
}
throw DateError.invalidDate
})
输出：
let decoder = JSONDecoder()
do {
let temp = try decoder.decode([Main].self, from: json)
// here we go, `temp` is an array of main object of the json
} catch {
print(error)
}
如果你想知道什么是json
let temp = try decoder.decode([Main].self, from: json)
我刚刚接受了附加的json响应并将其添加到Data对象中：
let json = """
[
{
"type": "temperatures",
"ts": "2017-11-08T16:43:59.558Z",
"source": "thermo-king",
"unit": {
"number": "1226000743"
},
"measurement": {
"ts": "2017-11-08T16:43:18.000Z",
"sensors": [
{
"address": "t1",
"description": "LFTest1",
"setpoints": [
{
"address": "s1",
"name": "LFSTest1"
}
]
},
{
"address": "t2",
"description": "LFTest2",
"setpoints": [
{
"address": "s2",
"name": "LFSTest2"
}
]
},
{
"address": "t3",
"description": "LFTest3",
"setpoints": [
{
"address": "s3",
"name": "LFSTest3"
}
]
},
{
"address": "t4",
"description": "LFTest4"
},
{
"address": "t5",
"description": "LFTest5"
},
{
"address": "t6",
"description": "LFTest6"
}
],
"sensor": {
"address": "t1",
"name": "LFTest1"
},
"setpoints": [
{
"address": "s1",
"name": "LFSTest1"
}
]
}
},
{
"type": "temperatures",
"ts": "2018-06-07T07:05:38.962Z",
"source": "1-wire",
"unit": {
"number": "1226000743"
},
"measurement": {
"ts": "2018-06-07T07:05:31.000Z",
"sensors": [
{
"address": "2839A5B104000004",
"description": "1-wire #1",
"status": "ok",
"temperature": 24.8
},
{
"address": "28EFBAB104000061",
"description": "1-wire #3",
"status": "ok",
"temperature": 24.5
},
{
"address": "2845F6B504000034",
"description": "1-wire #2",
"status": "ok",
"temperature": 24.5
}
],
"sensor": {
"address": "2839A5B104000004",
"name": "1-wire #1",
"status": "ok"
},
"temperature": 24.8
}
},
{
"type": "temperatures",
"ts": "2018-06-07T07:11:50.030Z",
"source": "vport",
"unit": {
"number": "1226000743"
},
"measurement": {
"ts": "2018-06-07T07:11:47.000Z",
"sensors": [
{
"address": "1036040010",
"description": "Vport 1-wire",
"status": "high",
"temperature": 26
}
],
"sensor": {
"address": "1036040010",
"name": "Vport 1-wire",
"status": "high"
},
"temperature": 26
}
}
]
""".data(using: .utf8)!
您可以轻松跳过那些未从服务器响应中获取的密钥。
Example JSON response is:
{
"isValid": false,
"pendingAttempts": 2
}
在这个json响应中缺少“id”字段，在我们的代码中我们已经声明了它。所以我们可以通过以下代码轻松跳过它。
//Code example
struct ResponseModel: Codable {
var id: String? //misng in response
var isValid: Bool?
var token: String?
//initializer
init(id: String?, isValid: Bool?, token: String?) {
self.id = id
self.isValid = isValid
self.token = token
}
//definging the coding keys
enum ResponseModelCodingKeys: String, CodingKey {
//The right hand side keys should be same as of json response keys
case id = "id"
case isValid = "isValid"
case token = "token"
}
//decoding initializer
init(from decoder: Decoder) throws {
var id: String?
var isValid: Bool?
var token: String?
let container = try decoder.container(keyedBy: ResponseModelCodingKeys.self) // defining our (keyed) container
do {
//if found then map
id = try container.decode(String.self, forKey: .id)
}
catch {
//not found then just set the default value
/******** This case will be executed **********/
id = ""
}
do {
//if found then map
isValid = try container.decode(Bool.self, forKey: .isValid)
}
catch {
//not found then just set the default value
isValid = false
}
do {
//if found then map
token = try container.decode(String.self, forKey: .token)
}
catch {
//not found then just set the default value
token = ""
}
//Initializing the model
self.init(id: id, isValid: isValid, token: token)
}
}
当我们对多个API有共同响应并且每个API都有一些缺失键时，此技术非常有用。