Swift Decodable with inconsistent API-CodePudding

I was wondering if there is a way to handle decoding JSON into a struct, when the API sending the JSON is potentially inconsistent with it's typing. In this case, it sometimes sends a property as an array, and other times as a string. I am not sure how to handle that, or if there is a nice way with Decodable. Example below. My Struct:

struct Movie: Decodable {
    let title: String
    let cast: [String]
    let director: [String]
}

The JSON:

[{
  "title": "Pulp Fiction",
  "cast": [
    "John Travolta",
    "Uma Thurman",
    "Samuel L. Jackson"
  ],
  "director": "Quentin Tarantino"
},
{
  "title": "Spider-Man: Into the Spider-Verse",
  "cast": [
    "John Travolta",
    "Uma Thurman",
    "Samuel L. Jackson"
  ],
  "director": [
    "Bob Persichetti",
    "Peter Ramsey",
    "Rodney Rothman"
  ]
}]

I am able to decode Spider-Man without an issue, but if there is only one director, it comes through as a string instead of an array. Is there a way to use Decodable for this? I know I could manually build the structs, but it would be nice to not have to. Unfortunately I have no control over the API here. Thanks in advance.

CodePudding user response：

The most versatile way to decode different types is an enum with associated values.

But in this case where the types are quite related you can also write a custom initializer, the struct member is named in plural form and is declared as array

struct Movie: Decodable {
    let title: String
    let cast: [String]
    let directors: [String]
    
    private enum CodingKeys : String, CodingKey { case title, cast, director }
    
    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        self.title = try container.decode(String.self, forKey: .title)
        self.cast = try container.decode([String].self, forKey: .cast)
        if let singleDirector = try? container.decode(String.self, forKey: .director) {
            self.directors = [singleDirector]
        } else {
            self.directors = try container.decode([String].self, forKey: .director)
        }
    }
}

CodePudding user response：

struct Movie: Codable {
    let title: String
    let cast: [String]
    let director: Director
}

enum Director: Codable {
    case string(String)
    case stringArray([String])

    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        if let x = try? container.decode([String].self) {
            self = .stringArray(x)
            return
        }
        
        if let x = try? container.decode(String.self) {
            self = .string(x)
            return
        }
        throw DecodingError.typeMismatch(Director.self, DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Wrong type for Director"))
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        switch self {
        case .string(let x):
            try container.encode(x)
        case .stringArray(let x):
            try container.encode(x)
        }
    }
}

typealias Movies = [Movie]