My struct isn't working for decodable - ios

Question

been using swift 3 for sometime, till i updated my Xcode which came with swift 4, and with that i had to start using encodable decodable , but i'm having a hard time generating structs to decode. This is the json i'm trying to turn into an object
{
"status": "true",
"message": "Valid request",
"data": {
"user_id": "16",
"first_name": "Hamidouh",
"last_name": "Semix",
"other_name": null,
"fullname": "Hamidouh Semix",
"alias": null,
"about": "",
"sex_id": "1",
"sex": "Male",
"birth_date": "1989-08-17 00:00:00",
"relation_status_id": null,
"relation_status": null,
"relation_user_id": null,
"relation_user_first_name": null,
"relation_user_last_name": null,
"relation_user_fullname": null,
"location": null,
"contact": null,
"profile_pic": "698",
"profile_folder_name": "profile-picture",
"profile_pic_filename": "PROFILE-IMG-UPLOAD-1-16-20171222101217.jpg",
"cover_pic": "697",
"cover_folder_name": "cover-picture",
"cover_pic_filename": "COVER-IMG-UPLOAD-1-16-20171222100128.png",
"followers_list": {
"user_11": {
"id": "11",
"datetime": "2018-02-20 19:09:44"
}
},
"following_list": {
"user_1": {
"id": "1",
"datetime": "2018-03-01 09:53:24"
},
"user_3": {
"id": "3",
"datetime": "2018-02-19 09:18:18"
},
"user_24": {
"id": "24",
"datetime": "2017-12-22 09:58:17"
},
"user_260": {
"id": "260",
"datetime": "2018-02-19 09:18:16"
}
},
"mutual_list": {
"user_78": {
"id": "78",
"datetime": "2017-12-08 12:05:23"
}
},
"request_counter": "0",
"dream_destination_list": null,
"hidden_content_list": null,
"email": "semixss.hamidouh#gmail.com",
"username": null,
"password": "84bcec2f89a4f8cdd17b4a98d1a6cbf69bc9efe657d36a09b2d423fa3030772ab8ba9e24",
"salt": "owkLO",
"social_media_auth": null,
"social_media_id": null,
"date_created": "2017-08-18 14:00:22",
"last_seen": "2018-03-16 13:53:57",
"is_suspended": null,
"is_notified": null,
"approve_token": "8f82fbac62ded7260a3faa45460719a1390e3e216c6ebf3c4794f2da627138b9",
"device_token": null,
"language_id": null,
"language_machine_name": null,
"language_label": null,
"active": "1"
}
}
currently these are the structs i've been able to generate for above json
struct user : Decodable {
let status: String
let message: String
let data: userData
}
struct userData : Decodable {
let user_id: Int
let first_name: String
let last_name: String
let other_name: String
let fullname: String
let alias: String
let about: String
let sex_id: Int
let sex: String
let birth_date: String
let relation_status_id: Int
let relation_status: String
let relation_user_id: Int
let relation_user_first_name: String
let relation_user_last_name: String
let relation_user_fullname: String
let location: String
let contact: String
let profile_pic: Int
let profile_folder_name: String
let profile_pic_filename: String
let cover_pic: Int
let cover_folder_name: String
let cover_pic_filename: String
let followers_list: Int
let following_list: Int
let mutual_list: Int
let request_counter: Int
let dream_destination_list: Int
let hidden_content_list: Int
let email: String
let username: String
let password: String
let salt: String
let social_media_auth: String
let social_media_id: Int
let date_created: String
let last_seen: String
let is_suspended: String
let is_notified: String
let approve_token: String
let device_token: String
let language_id: Int
let language_machine_name: String
let language_label: String
let active: Int
}
This is the decoding code i've written to try and parse this
//send request to server
guard let loginUrl = URL(string: "https://xxxxxx.com/api/index.php/Auth/login") else {return}
//request url
var request = URLRequest(url: loginUrl)
// method to pass data
request.httpMethod = "POST"
let body = "username=\(usernameVar)&password=\(passwordVar)"
request.httpBody = body.data(using: String.Encoding.utf8)
//launch session
let session = URLSession.shared
let task = session.dataTask(with: request) { (data, response, error) in
guard let data = data else {return}
do {
//let json = try JSONSerialization.jsonObject(with: data, options: [])
//print(json)
let userDetails = try JSONDecoder().decode(user.self, from: data)
for details in userDetails {
print(details.message)
}
}catch{
print(error)
}
}
task.resume()
This is the error
typeMismatch(Swift.Array, Swift.DecodingError.Context(codingPath: [], debugDescription: "Expected to decode Array but found a dictionary instead.", underlyingError: nil))

Answer 1

You should change your error message to a more helpful error message Lol.
You haven't accounted for optional values in your json. Remember there is a difference between String and String? there are several values in your json payload that return nil. In your swift struct you need to mark those fields as Optionals.
You also have mismatched Types. All of your returned types are String or String? not Int. Those are just numbers returned as String?. There are also Dictionary types nested in this payload as well. The followers_list is a dictionary so you need to make a new struct with those properties, called List and in your UserData struct, set the type of those "lists" to [String:List]
Also when you're confused about what kind of error is being thrown while decoding, (and most of the CocoaTouch Framework) those are NSErrors. You can print the value of the error to the console and it'll tell you exactly what error is exiting the scope. IE:
valueNotFound(Swift.String, Swift.DecodingError.Context(codingPath: [__lldb_expr_20.user.(CodingKeys in _992B1F7B4C3E0BAC48AEA280B9410D72).data, __lldb_expr_20.userData.,
debugDescription: "Expected String value but found null instead.", underlyingError: nil))
The above error message tells you that CodingKey...userData was set to expect a String but there was null (nil).
Heres what your current struct should look like:
struct User : Decodable {
let status: String
let message: String
let data: userData
}
struct List: Decodable {
var id: String?
var datetime: String?
}
struct UserData : Decodable {
let user_id: String
let first_name: String
let last_name: String
let other_name: String?
let fullname: String
let alias: String?
let about: String
let sex_id: String
let sex: String
let birth_date: String
let relation_status_id: String?
let relation_status: String?
let relation_user_id: String?
let relation_user_first_name: String?
let relation_user_last_name: String?
let relation_user_fullname: String?
let location: String?
let contact: String?
let profile_pic: String
let profile_folder_name: String
let profile_pic_filename: String
let cover_pic: String
let cover_folder_name: String
let cover_pic_filename: String
let followers_list: [String:List]
let following_list: [String:List]
let mutual_list: [String:List]
let request_counter: String
let dream_destination_list: List?
let hidden_content_list: List?
let email: String
let username: String?
let password: String?
let salt: String
let social_media_auth: String?
let social_media_id: String?
let date_created: String
let last_seen: String
let is_suspended: String?
let is_notified: String?
let approve_token: String
let device_token: String?
let language_id: String?
let language_machine_name: String?
let language_label: String?
let active: String
}
Loose the snake case and use CodingKeys to follow Swift Naming Conventions or use a public struct with the values you care about(You don't have to model the entire JSON payload) with a private struct that models the JSON and set the values with a custom init(from decoder: Decoder) using this answer.