Codable for mapping different key-values with Single Model - swift

Question

JSON 1:
{
"error_code" : 100,
"error_message" : "Something went wrong"
}
JSON 2
{
"failure_code" : 100,
"failure_message" : "Something not right here"
}
Change to below code to map above JSON:
class Failure: Codable {
var code: Int?
var message: String?
private enum CodingKeys: String, CodingKey {
case code
case message
}
}
How can we do it?

Answer 1

Here is one way you could do it:
import Cocoa
import Foundation
struct CustomError {
var code: Int
var message: String
}
extension CustomError : Decodable {
private enum FirstKeys: String, CodingKey {
case error_code, error_message
}
private enum SecondKeys: String, CodingKey {
case failure_code, failure_message
}
init(from decoder: Decoder) throws {
do {
print("Case 1")
let container = try decoder.container(keyedBy: FirstKeys.self)
code = try container.decode(Int.self, forKey: .error_code)
message = try container.decode(String.self, forKey: .error_message)
print("Error with code: \(code) and message: \(message)")
} catch {
print("Case 2")
let container = try decoder.container(keyedBy: SecondKeys.self)
code = try container.decode(Int.self, forKey: .failure_code)
message = try container.decode(String.self, forKey: .failure_message)
print("Error with code: \(code) and message: \(message)")
}
}
}
let json = """
{
"failure_code": 1,
"failure_message": "test"
}
""".data(using: .utf8)!
let error = try JSONDecoder().decode(CustomError.self, from: json)
print(error)
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Answer 2

Write a custom init method which handles the cases. A class is not needed.
struct Failure: Decodable {
var code: Int
var message: String
private enum CodingKeys: String, CodingKey {
case error_code, error_message
case failure_code, failure_message
}
init(from decoder: Decoder) throws {
let container = try decoder.container(keyedBy: CodingKeys.self)
do {
code = try container.decode(Int.self, forKey: .error_code)
message = try container.decode(String.self, forKey: .error_message)
} catch DecodingError.keyNotFound {
code = try container.decode(Int.self, forKey: .failure_code)
message = try container.decode(String.self, forKey: .failure_message)
}
}
}