Convert received Int to Bool decoding JSON using C

问题:

I have structure like this:

struct JSONModelSettings {
    let patientID : String
    let therapistID : String
    var isEnabled : Bool

    enum CodingKeys: String, CodingKey {
        case settings // The top level "settings" key
    }

    // The keys inside of the "settings" object
    enum SettingsKeys: String, CodingKey {
        case patientID = "patient_id"
        case therapistID = "therapist_id"
        case isEnabled = "is_therapy_forced"
    }
}

extension JSONModelSettings: Decodable {
    init(from decoder: Decoder) throws {

        // Extract the top-level values ("settings")
        let values = try decoder.container(keyedBy: CodingKeys.self)

        // Extract the settings object as a nested container
        let user = try values.nestedContainer(keyedBy: SettingsKeys.self, forKey: .settings)

        // Extract each property from the nested container
        patientID = try user.decode(String.self, forKey: .patientID)
        therapistID = try user.decode(String.self, forKey: .therapistID)
        isEnabled = try user.decode(Bool.self, forKey: .isEnabled)
    }
}

and JSON in this format (structure used to pull keys from setting without extra wrapper):

{
  "settings": {
    "patient_id": "80864898",
    "therapist_id": "78920",
    "enabled": "1"
  }
}

Question is how can i convert "isEnabled" to Bool, (getting 1 or 0 from API) When im trying to parse response im getting error: "Expected to decode Bool but found a number instead."

回答1:

My suggestion is: don't fight the JSON. Get it into a Swift value as quickly and with little fuss as possible, then do your manipulation there.

You can define a private internal structure to hold the decoded data, like this:

struct JSONModelSettings {
    let patientID : String
    let therapistID : String
    var isEnabled : Bool
}

extension JSONModelSettings: Decodable {
    // This struct stays very close to the JSON model, to the point
    // of using snake_case for its properties. Since it's private,
    // outside code cannot access it (and no need to either)
    private struct JSONSettings: Decodable {
        var patient_id: String
        var therapist_id: String
        var enabled: String
    }

    private enum CodingKeys: String, CodingKey {
        case settings
    }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        let settings  = try container.decode(JSONSettings.self, forKey: .settings)
        patientID     = settings.patient_id
        therapistID   = settings.therapist_id
        isEnabled     = settings.enabled == "1" ? true : false
    }
}

---

Other JSON mapping frameworks, such as ObjectMapper allows you to attach a transform function to the encoding/decoding process. It looks like Codable has no equivalence for now.

回答2:

In those cases I like to keep the model like the JSON data, so in your case Ints. Than I add computed properties to the model to convert into Booleans etc

struct Model {
   let enabled: Int

   var isEnabled: Bool {
       return enabled == 1
   }
}

回答3:

Decode as a String and then convert it to Bool, just modifying some lines of your code:

("0" is a JSON string, and cannot be decoded as an Int.)

struct JSONModelSettings {
    let patientID : String
    let therapistID : String
    var isEnabled : Bool

    enum CodingKeys: String, CodingKey {
        case settings // The top level "settings" key
    }

    // The keys inside of the "settings" object
    enum SettingsKeys: String, CodingKey {
        case patientID = "patient_id"
        case therapistID = "therapist_id"
        case isEnabled = "enabled"//### "is_therapy_forced"?
    }
}

extension JSONModelSettings: Decodable {
    init(from decoder: Decoder) throws {

        // Extract the top-level values ("settings")
        let values = try decoder.container(keyedBy: CodingKeys.self)

        // Extract the settings object as a nested container
        let user = try values.nestedContainer(keyedBy: SettingsKeys.self, forKey: .settings)

        // Extract each property from the nested container
        patientID = try user.decode(String.self, forKey: .patientID)
        therapistID = try user.decode(String.self, forKey: .therapistID)

        //### decode the value for "enabled" as String
        let enabledString = try user.decode(String.self, forKey: .isEnabled)
        //### You can throw type mismatching error when `enabledString` is neither "0" or "1"
        if enabledString != "0" && enabledString != "1" {
            throw DecodingError.typeMismatch(Bool.self, DecodingError.Context(codingPath: user.codingPath + [SettingsKeys.isEnabled], debugDescription: "value for \"enabled\" needs to be \"0\" or \"1\""))
        }
        //### and convert it to Bool
        isEnabled = enabledString != "0"
    }
}