swift4 encoding decoding for model class of nested json parsing - json

Question

I have a model class of swift which was created based on a nested json response, it follows like below
struct RootClass : Codable {
let details : String?
let itemCount : Int?
let list : [List]?
enum CodingKeys: String, CodingKey {
case details = "Details"
case itemCount = "ItemCount"
case list = "List"
}
init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
details = try values.decodeIfPresent(String.self, forKey: .details)
itemCount = try values.decodeIfPresent(Int.self, forKey: .itemCount)
list = try values.decodeIfPresent([List].self, forKey: .list)
}
}
struct List : Codable {
let companyID : Int?
let employeeCount : Int?
let employeeUser : EmployeeUser?
enum CodingKeys: String, CodingKey {
case companyID = "CompanyID"
case employeeCount = "EmployeeCount"
case employeeUser = "EmployeeUser"
}
init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
companyID = try values.decodeIfPresent(Int.self, forKey: .companyID)
employeeCount = try values.decodeIfPresent(Int.self, forKey: .employeeCount)
employeeUser = try EmployeeUser(from: decoder)
}
}
struct EmployeeUser : Codable {
let mobileNumber : String?
let name : String?
enum CodingKeys: String, CodingKey {
case mobileNumber = "MobileNumber"
case name = "Name"
}
init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
mobileNumber = try values.decodeIfPresent(String.self, forKey: .mobileNumber)
name = try values.decodeIfPresent(String.self, forKey: .name)
}
}
and my json response is
{
"Details": null,
"List": [
{
"CompanyID": 140,
"EmployeeUser": {
"Name": " raghu2",
"MobileNumber": "8718718710"
},
"EmployeeCount": 0
},
{
"CompanyID": 140,
"EmployeeUser": {
"Name": "new emp reg",
"MobileNumber": "1"
},
"EmployeeCount": 0
}
],
"ItemCount": 0
}
I am trying to parse it like
guard let data = data else { return }
do {
let decoder = JSONDecoder()
let gitData = try decoder.decode(RootClass.self, from: data)
print(gitData.itemCount ?? "")
print(gitData.list![0].employeeUser?.mobileNumber ?? "")
}
catch let err {
print("Err", err)
}
I am able to get the values of root class and list but I am getting nil values under employee user section.

Answer 1

Your code a few problems:
All your keys are optional. The vendor API will tell you what keys are always present and which one are optional. Follow that.
decodeIfPresent will silently fail if it cannot decode a key. When debugging your app, you want things to fail with a bang so you can fix the error before going to production.
You wrote way more code than needed. All those init(from decoder: ) functions are not needed. One one did cause your problem.
Your problem was caused by this line:
struct List : Codable {
init(from decoder: Decoder) throws {
...
employeeUser = try EmployeeUser(from: decoder)
}
}
You are asking Swift to decode to same JSON to a List and a EmployeeUser object. Obviously, that's not valid. But when you decode list inside RootClass, you call decodeIfPresent:
// In Rootclass
list = try values.decodeIfPresent([List].self, forKey: .list)
This call silently failed and you never knew what the problem was!
Solution
Change how you initialize employeeUser to this:
employeeUser = try values.decodeIfPresent(EmployeeUser.self, forKey: .employeeUser)
But the most elegant solution is to delete all those init(from decoder: ). The compiler will synthesize them for you.
And finally, fix those optionals!