How to decode single unusual property among many Decodable Swift?

Question

I have a struct conforming to Decodable. It has 50 String properties and only one Bool. That bool is coming from server like a string "false"/"true" or sometimes like as integer 0/1, so cannot be decoded from the box. How can I make it decoding but not write huge amount of manual decoding of all that 50 String properties? Maybe somehow override decodeIfPresent for Bool, but I could not make it working. How I can avoid creating init with decoding everything and all that stuff manually and only handle that one Bool? Without computed property if possible.

struct Response: Decodable {
    var s1: String
    var s2: String
    var s3: String
    //...........
    var s50: String
    var b1: Bool
    var b2: Bool
}

Here is json example:

{
    "s1":"string"
    "s2":"string"
    "s3":"string"
    //..........
    "s50":"string"
    "b1":"true"
    "b2":"0"
}

Tried this but does not work(((

extension KeyedDecodingContainer { //Doesn't work, no execution
    func decodeIfPresent(_ type: Bool.Type, forKey key: K) throws -> Bool {
        return try! self.decodeIfPresent(Bool.self, forKey: key)
    }
    func decodeIfPresent(_ type: Bool.Type, forKey key: K) throws -> Bool? {
        return try? self.decodeIfPresent(Bool.self, forKey: key)
    }
}

Answer 1

One way to solve this is to write a property wrapper that handles the custom decoding, like this:

@propertyWrapper
struct FunnyBool: Decodable {
    var wrappedValue: Bool

    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        if let value = try? container.decode(Bool.self) {
            wrappedValue = value
        }
        else if
            let string = try? container.decode(String.self),
            let value = Bool(string)
        {
            wrappedValue = value
        }
        else if
            let int = try? container.decode(Int.self),
            let value = int == 0 ? false : int == 1 ? true : nil
        {
            wrappedValue = value
        }
        else {
            // Default...
            wrappedValue = false
        }
    }
}

Use it like this:

struct Response: Decodable {
    var s1: String
    var s2: String
    @FunnyBool var b: Bool
}

let json = #"{ "s1": "hello", "s2": "world", "b": 1 }"#
let response = try! JSONDecoder().decode(Response.self, from: json.data(using: .utf8)!)
dump(response)

Playground output:

▿ __lldb_expr_11.Response
  - s1: "hello"
  - s2: "world"
  ▿ _b: __lldb_expr_11.FunnyBool
    - wrappedValue: true