same struct for sending and receiving json data in swift - ios

Question

I want to use the same model struct for sending parameters and receiving JSON response from an API.
I want to send email and password and receive JSON response message.
But when I declare a property referencing another model in my user model, I am forced to provide a value.
My API does not return the parameters email and password, it simply returns an array if login is unsuccessful and returns the user info on successful login.
this is the json response on error :
Optional({
errors = {
msg = "USER_DOES_NOT_EXIST";
};
this is my model I used to post:
struct LoginUser: Codable {
let email: String?
let password: String?
}
this is the response on successful login:
Optional({
token = 267e6a9d5a128fb1f44e670fcd89793af50fa9a831e6ae7dc2f0592b508bd224a71290fbdf1619cf52ed0f2c034b26383b915343f3822a52e1386c042484744b71811f80d3cb663fc76a6cc74d4866737421e3b9d62e35b415c0f7c385e5c70d472a5facf7f0101165d321c35eb20ae5f8bb32f06120e66a42de47c79a7587a2aa7f81f35c3821b9418e0c9142a7ec2b67b9755d3e17753dd8f1cdf3f71c0816627e2be26485f9b50ee1ad96a867856f0de736963c5ff59e9e37e92d5f3386f7;
user = {
"_id" = 5e52c0c5cf65d33726a98590;
email = "test7#gmail.com";
"first_name" = gagz;
"last_name" = bhullar;
verified = 0;
};
})
I want to modify my loginUser model such that it can both receive and send data.
is it possible?
if not, why?

Answer 1

For an API which returns two different models on success and failure I highly recommend to use an enum with associated values. The benefit is you get rid of the tons of optionals (and if let expressions) and you can use a descriptive switch for the success and failure cases.
enum Response : Decodable {
case success(UserResponse)
case failure(ErrorResponse)
init(from decoder: Decoder) throws {
let container = try decoder.singleValueContainer()
do {
let userData = try container.decode(UserResponse.self)
self = .success(userData)
} catch DecodingError.typeMismatch {
let errorData = try container.decode(ErrorResponse.self)
self = .failure(errorData)
}
}
}
And these are the corresponding structs
struct ErrorResponse: Decodable {
let errors: [String:String]
}
struct UserResponse: Decodable {
let token : String
let user: User
}
struct User: Decodable {
private enum CodingKeys : String, CodingKey {
case id = "_id"
case email
case firstName = "first_name"
case lastName = "last_name"
case verified
}
let id, email, firstName, lastName : String
let verified : Int // maybe Bool
}
To send only two key-value pairs an extra struct and Codable is overkill. Create a temporary [String:String] dictionary and encode it with JSONSerialization or create the JSON Data directly for example
func jsonSendData(email: String, password: String) -> Data {
let jsonString =
"""
{"email":"\(email)","password":"\(password)"}
"""
return Data(jsonString.utf8)
}

Answer 2

Although it is recommended to create separate model for handling the failure and success cases, still if you want to create a single model, you can do it like so,
struct LoginUser: Codable {
let email, password, token, id, firstName, lastName: String?
let verified: Int?
let errorMessage: String?
enum CodingKeys: String, CodingKey {
case email, token, _id, firstName, lastName, verified, user
case errors, msg
case password
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
token = try container.decodeIfPresent(String.self, forKey: .token)
if container.contains(.user) {
let user = try container.nestedContainer(keyedBy: CodingKeys.self, forKey: .user)
id = try user.decodeIfPresent(String.self, forKey: ._id)
email = try user.decodeIfPresent(String.self, forKey: .email)
firstName = try user.decodeIfPresent(String.self, forKey: .firstName)
lastName = try user.decodeIfPresent(String.self, forKey: .lastName)
verified = try user.decodeIfPresent(Int.self, forKey: .verified)
errorMessage = nil
} else if container.contains(.errors) {
let errors = try container.nestedContainer(keyedBy: CodingKeys.self, forKey: .errors)
errorMessage = try errors.decodeIfPresent(String.self, forKey: .msg)
id = nil
email = nil
firstName = nil
lastName = nil
verified = nil
} else {
id = nil
email = nil
firstName = nil
lastName = nil
verified = nil
errorMessage = nil
}
password = nil
}
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(email, forKey: .email)
try container.encode(password, forKey: .password)
//add the keys that you want to send in the request...
}
}
Since, you haven't added the the JSON that you want to send in the request, I've assumed that you're only sending email and password in the request. You can add more in the above encode(to:) method.