Initialize Swift class with AnyObject? from NSJSONSerialization

Question

I am using NSJSONSerialization in Swift 1.2 to parse some json that is returned from an API response.

var err: NSError?
let opts = NSJSONReadingOptions.AllowFragments
let json: AnyObject? = NSJSONSerialization.JSONObjectWithData(jsonData!, options: opts, error: &err)

The parsed json is provided as AnyObject?. I would like to use this optional to initialize a class object which can be used as the model data in an application.

class Alerts {
    let type: String
    let date: String
    let description: String
    let expires: String
    let message: String

    init(json: AnyObject) {
        if let
        jsonDict = json as? [String: AnyObject],
        alertsArray = jsonDict["alerts"] as? [AnyObject],
        alertsDict = alertsArray[0] as? [String: AnyObject],
        type = alertsDict["type"] as? String,
        date = alertsDict["date"] as? String,
        description = alertsDict["description"] as? String,
        expires = alertsDict["expires"] as? String,
        message = alertsDict["message"] as? String
        {
            self.type = type
            self.date = date
            self.description = description
            self.expires = expires
            self.message = message
        }
        else
        {
            self.type = "err"
            self.date = "err"
            self.description = "err"
            self.expires = "err"
            self.message = "err"
        }
    }
}

// example of creating a data model from the json
let alerts = Alerts(json: json!)
alerts.type
alerts.date
alerts.description
alerts.expires
alerts.message

Since NSJSONSerialization returns an optional, I have to check for the existence of each value type as I extract the json data. As you can see in the above code, I used the improved optional bindings from Swift 1.2 to clean up the init method. Without using third-party libraries, is there anything else I can do to the class model (enums, structs, type aliases) to make it more readable? Should I use a struct for the model data instead of a class? Would it be possible to create a custom type using an enum or struct to represent a json object?

Answer 1

So without using third party libraries, the if let trees are usually the best practice, which you have shown. To help you later down the road, maybe recreate your object hierarchy in JSON as a Struct model in Swift. Something like:

var json = JSON(JSONData.sharedjson.jsonRaw!)
var mongoIdTest = json["resultset"]["account"]["mongoId"].string

struct Root {
    var timestamp: Int?
    var resultset = ResultSet()

    init() {
        self.timestamp = json["timestamp"].int
        println(json)
    }

}

struct ResultSet {
    var alert: String?

    var account = Account()
    var customer = Customer()

    init() {

    }


}

struct Account {
    var mongoId: String?

    init() {
        mongoId = json["resultset"]["account"]["mongoId"].string
    }
}

struct Locations {

}

struct Customer {
    var account: String?
    var address: String?
    var id: String?
    var loginId: String?
    var mongoId: String?
    var name: String?

    var opco = Opco()

    init() {
        account = json["resultset"]["customer"]["account"].string
        address = json["resultset"]["customer"]["address"].string
        id = json["resultset"]["customer"]["id"].string
        loginId = json["resultset"]["customer"]["loginId"].string
        mongoId = json["resultset"]["customer"]["mongoId"].string
        name = json["resultset"]["customer"]["name"].string
    }

}

struct Opco {
    var id: String?
    var phone: String?
    var cutOffTime: String?
    var name: String?
    var payerId: String?

    init() {
        id = json["resultset"]["customer"]["opco"]["id"].string
        phone = json["resultset"]["customer"]["opco"]["phone"].string
        cutOffTime = json["resultset"]["customer"]["opco"]["cutOffTime"].string
        name = json["resultset"]["customer"]["opco"]["name"].string
        payerId = json["resultset"]["customer"]["opco"]["payerId"].string
    }
}

This way you can still use autocomplete and dot notation to navigate through your hierarchy.

Edit: I have a data structure from an actual project I've worked on added to the answer, hopefully this gives a better idea. Keep in mind that I'm using SwiftyJSON for the JSON() call.

Edit 2:

This is a method I found for getting JSON info into a Swift dictionary without the use of some other library. I'm not sure there is another way to do it that's easier without the use of third party libraries.

var urlToRequest = "https://EXAMPLE.com/api/account.login?username=MY_USERNAME&password=Hunter2"

if let json = NSData(contentsOfURL: NSURL(string: urlToRequest)!) {

    // Parse JSON to Dictionary
    var error: NSError?
    let boardsDictionary = NSJSONSerialization.JSONObjectWithData(json, options: NSJSONReadingOptions.MutableContainers, error: &error) as? Dictionary<String, AnyObject>
    fulljson = boardsDictionary

    // Display all keys and values
    println("Keys in User Data:")
    for (key, value) in boardsDictionary! {
        println("\(key)-------\(value)")
    }

    println(fulljson?["resultset"])
}
else {
    println("Test JSON nil: No Connection?")
}

That dictionary will be the input for your Structs.