Swift 4 JSON 解码根数组
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【中文标题】Swift 4 JSON 解码根数组【英文标题】:Swift 4 JSON Decode Root Array 【发布时间】:2018-03-20 14:38:23 【问题描述】:我在使用 Swift 4 解码功能解码 JSON 响应时遇到问题。 我有主结构,它有一个内部结构 var hr_employees: [Employee]? = []。问题是 JSON 没有映射 'var hr_employees: [Employee]? = []。
我得到了三个根值 response_status、access_level、session_token 的正确值。
////////////////////////////////////////////////////////////
struct EmployeeData: Codable
var response_status:Int=0
var access_level:Int=0
var session_token:String=""
var hr_employees: [Employee]? = []
private enum CodingKeys: String, CodingKey
case response_status="response_status"
case access_level="access_level"
case session_token="session_token"
case hr_employees="hr_employees"
init()
init(from decoder: Decoder) throws
let values = try decoder.container(keyedBy: CodingKeys.self)
response_status = try values.decode(Int.self, forKey: .response_status)
do
session_token = try values.decode(String.self, forKey: .session_token)
catch
print( "No value associated with key title (\"session_token\").")
do
access_level = try values.decode(Int.self, forKey: .access_level)
catch
print( "No value associated with key access_level ")
///////////////内部结构///////////////////
struct Employee: Codable
var userId:Int=0
var nameFirst:String=""
var nameLast:String=""
var position:String=""
var company:String=""
var supervisor:String=""
var assistant:String=""
var phone:String=""
var email:String=""
var address:String=""
var gender:String=""
var age:Int=0
var nationality:String=""
var firstLanguage:String=""
var inFieldOfView:String = "0"
var photo:String="user-default"
var status:String="3"
///////////下面是JSON///////////////////
"response_status":1
,"access_level":2
,"hr_employees":[
"user_id":4226
,"name_last":"Sampe"
,"name_first":"Frederica"
,"position":"Systems Maint"
,"phone":"123456"
,"email":"omega@demo.mobile"
,"address":"00100 Helsinki 1"
,"age":67
,"company":"Omega Enterprise"
,
"user_id":5656
,"name_last":"Aalto"
,"name_first":"Antero"
,"position":"Programming Methodology and Languages Researcher"
,"supervisor":"Mayo Georgia"
,"phone":"123456"
,"email":"omega@demo.mobile"
,"address":"00100 Finland "
,"age":51
,"company":"Omega Fire Related Equipment"
]
【问题讨论】:
【参考方案1】:一个问题是 JSON 中的内容与您对 Employee 的定义不匹配。例如,nameFirst
不存在,name_first
存在。
另一个是你有一个init(from:)
的自定义实现,它永远不会获取hr_employees
值!
【讨论】:
【参考方案2】:有很多事情需要你改进:
-
您的
Struct
s 可以改进以利用Codable
协议的自动化功能。
您需要了解为什么要使用CodingKeys
枚举
在你的情况下......也是最好的地方(提示:在Struct
本身内)
您需要知道哪些参数需要是可选的以及为什么
这当然取决于你的 json 结构
如果参数要具有默认值,那么您需要遵循一个完全不同的过程;就像拥有自己的init(from:Decoder)
您在一定程度上需要,但并不能真正处理当前状态下的所有内容
根据您给定的 JSON 示例,您可以简单地执行以下操作。但是...请注意,这并非旨在提供默认值。即,如果 json 中缺少某个键,例如 status
,那么 Employee
结构中的参数 status
将是 nil
,而不是默认值 "3"
。
struct EmployeeData: Codable
var responseStatus: Int
var accessLevel: Int
/*
sessionToken is optional because as per your JSON
it seems it not always available
*/
var sessionToken: String?
var hrEmployees: [Employee]
/*
CodingKeys is inside the struct
It's used if the JSON key names are different than
the ones you plan to use.
i.e. JSON has keys in snake_case but we want camelCase
*/
enum CodingKeys: String, CodingKey
case responseStatus = "response_status"
case accessLevel = "access_level"
case sessionToken = "session_token"
case hrEmployees = "hr_employees"
struct Employee: Codable
var userId: Int
var nameFirst: String
var nameLast: String
var position: String
var company: String
var supervisor: String?
var assistant: String?
var phone: String
var email: String
var address: String
var gender: String?
var age: Int
var nationality: String?
var firstLanguage: String?
var inFieldOfView: String?
var photo: String?
var status: String?
enum CodingKeys: String, CodingKey
case userId = "user_id"
case nameFirst = "name_first"
case nameLast = "name_last"
case firstLanguage = "first_language"
case inFieldOfView = "in_field_of_view"
/*
Keys names that are same in json as well as in your
model need not have a raw string value
but must be defined if it's to be encoded/decoded
from the json else it can be omitted and a default
value will be required which won't affect the encoding
or decoding process
*/
case position
case company
case supervisor
case assistant
case phone
case email
case address
case gender
case age
case nationality
case photo
case status
检查:
do
let employeeData = try JSONDecoder().decode(EmployeeData.self,
from: jsonAsData)
print(employeeData)
catch
/*
If it comes here then debug, it's most probably nil keys
meaning you need more optional parameters in your struct
*/
print(error)
如果你想在你的Struct
中使用默认值,而上面的例子对你来说是一个破坏者,那么请检查以下答案:
【讨论】:
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