Convert an Int JSON value to String enum case - swift

Question

Here's an simplified version of the class:
class Movie: Codable {
var name: String
var genre: MovieGenre
init(name: String, genre: MovieGenre) {
self.name = name
self.genre = genre
}
}
enum MovieGenre: String, Codable {
case action
case drama
case horror
}
And the JSON:
{
"name" : "Test",
"genre" : 1
}
I know the relation between the JSON genre value and the MovieGenre enum is:
1 = action
2 = drama
3 = horror
Using JSONDecoder, how can I convert the JSON genre Int value to my enum MovieGenre?
I would like not to have to write an init from decoder, because it would be very verbose having to convert each attribute manually.
Here's an example:
let movie = Movie(name: "Test", genre: .action)
let jsonEncoder = JSONEncoder()
let jsonDecoder = JSONDecoder()
do {
// encoding
let jsonData = try jsonEncoder.encode(movie)
let jsonString = String(data: jsonData, encoding: .utf8)
print("JSON String : " + jsonString!) // prints: JSON String : {"name":"Test","genre":"action"}
// decoding
let json = "{\"name\":\"Test\",\"genre\":1}".data(using: .utf8)!
_ = try jsonDecoder.decode(Movie.self, from: json)
} catch {
print(error) // prints: typeMismatch(Swift.String, Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "genre", intValue: nil)], debugDescription: "Expected to decode String but found a number instead.", underlyingError: nil))
}

Answer 1

Your type for your enum does not match with the type in the JSON.
I changed the Type for your enum to Int and set the initial value for action (as the default would be 0) and got the expected result without custom decoding.
Trying this in a playground:
import UIKit
import PlaygroundSupport
let jsonData = """
{
"name" : "Test",
"genre" : 1
}
""".data(using: .utf8)!
class Movie: Codable {
var name: String
var genre: MovieGenre
init(name: String, genre: MovieGenre) {
self.name = name
self.genre = genre
}
}
enum MovieGenre: Int, Codable {
case action = 1
case drama
case horror
}
let decoder = JSONDecoder()
let result = try? decoder.decode(Movie.self, from: jsonData)
print(result?.name)
print(result?.genre)
print(result?.genre.rawValue)
Output is:
Optional("Test")
Optional(__lldb_expr_39.MovieGenre.action)
Optional(1)
This should also encode in the same way.