json - 使用 Codable 问题解码 JSON。keyNotFound 错误信息
问题描述
我在解码 JSON 时遇到问题。我正在尝试用
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,如果我试图解码我的 JSON,我会收到非常清楚的错误消息
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
}
}
]
所以我可以猜测这是因为数据的第一部分而给出的错误,但是应该省略它并与其余部分一起生成数据吗?
解决方案
跟踪您的问题后,我认为有几个问题,首先:
您没有声明选项:
根据所附的json,似乎有一些属性并不总是存在,例如:
status
=>VportSensor
。temperature
=>Measurement
。temperature
=>VportSensor
。temperature
=>setpoints
。
您需要确保将任何可能未收到的属性声明为可选。
此外,可编码结构的实现:
实现的结构似乎不是典型的 json 响应结构,请确保声明您的可编码结构与接收到的 json 结构匹配。
注意:
lastUpdate
并且description
不用于VportSensor
.- 根据我的回答,没有必要
TemperatureSensor
...
小费:
在使用日期(例如ts
)时,您应该直接将其声明为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,你可以在这个答案中找到如何去做。
执行:
根据上面的描述,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)
}
如果你想知道里面有json
什么
let temp = try decoder.decode([Main].self, from: json)
我只是将附加的 json 响应添加到Data
Object 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)!
推荐阅读
- git - 无法在 gitlab ci 管道中推送 git 标签
- javascript - 从后端代码向 bootstrap-notify 发送数据
- mysql - 如何使用 ActiveRecord 进行两个连接并执行单个活动记录查询?
- regex - 如何sed或perl用不带引号的点和斜杠替换文本?
- c++ - 如何使用级联阴影映射制作软阴影?
- typescript - 在带有 Typescript 的 React Native StyleSheet 中使用函数
- oracle - 编译过程时没有足够的值
- sql - 我也不明白 ORA-01779 指的是什么列
- python - Python Plotnine - 创建堆积条形图
- sql-server - 优化单个表上具有多个连接的查询