swift: cast incoming json array to dictionary and object

Question

I am toying around/learning Swift and JSON atm and have problems correctly casting around my responses.

So, what I am trying to achieve is displaying a list of "posts" via Alamofire request. I have no problems displaying "first-level" json items like the post-ID or the "message", but when it comes to the author array I am kinda lost.

the json response comes in as an Array with no name, hence the first [

[
-{
__v: 1,
_id: "54428691a728c80424166ffb",
createDate: "2014-10-18T17:26:15.317Z",
message: "shshshshshshshhshshs",
-author: [
-{
_id: "54428691a728c80424166ffa",
userId: "543270679de5893d1acea11e",
userName: "foo"
}
]
} 

Here is my corresponding VC:

    Alamofire.request(.GET, "\(CurrentConfiguration.serverURL)/api/posts/\(CurrentConfiguration.currentUser.id)/newsfeed/\(CurrentConfiguration.currentMode)",encoding:.JSON)
            .validate()
            .responseJSON {(request, response, jsonData, error) in

                let JSON = jsonData as? NSArray
                self.loadPosts(JSON!)
        }

        tableView.delegate = self

        tableView.dataSource = self

    }

    func loadPosts(posts:NSArray) {
        for post in posts {
            let id = post["_id"]! as NSString!
            let message = post["message"]! as NSString!

            var authorArray = post["author"]! as? [Author]!
            println(authorArray)

            var author:Author = Author()
            author.userName = "TEST ME"

            var postObj:Post = Post()
            postObj.id = id
            postObj.message = message
            postObj.author = author
            uppDatesCollection.append(postObj)
        }
        println(self.uppDatesCollection.count)
        dispatch_async(dispatch_get_main_queue()) {
            self.tableView.reloadData()
        }
    }

my Models for Post

class Post {
    var id:String!
    var message:String!
    var createDate: NSDate!

    var author:Array<Author>!

    init () {

    }
} 

and Author

class Author {
        var id:String?
        var userId:String?
        var userName:String?

        init () {
    }

What is the best Approach here? Should you recast the returning Array as a Dictionary and then Access it via .valueforkey? Do you somehow iterate over the array to get this stuff out?

Obviously you can not say author.name = authorArray[3] as String

Answer 1

Let's say you had Post class like so:

class Post : Printable {
    var identifier:String!
    var message:String!
    var createDate: NSDate!
    var authors:[Author]!

    var description: String { return "<Post; identifier = \(identifier); message = \(message); createDate = \(createDate); authors = \(authors)" }
}

Your JSON has only one author in it, but given that it appears to be an array in the JSON, I assume it should be an array in the object model, too, as shown above. The Author class might be defined as so:

class Author : Printable {
    var identifier:String!
    var userId:String!
    var userName:String!

    var description: String { return "<Author; identifier = \(identifier); userId = \(userId); userName = \(userName)>" }
}

I wasn't sure why you made some of your optionals implicitly unwrapped (defined with !) and others not (defined with ?), so I just made them all implicitly unwrapped. Adjust as appropriate to your business rules.

Also, let's say your JSON looked like so (I wasn't quite sure what to make of the - in the JSON in your question, so I cleaned it up and added a second author):

[
    {
        "__v": 1,
        "_id": "54428691a728c80424166ffb",
        "createDate": "2014-10-18T17:26:15.317Z",
        "message": "shshshshshshshhshshs",
        "author": [
            {
                "_id": "54428691a728c80424166ffa",
                "userId": "543270679de5893d1acea11e",
                "userName": "foo"
            },
            {
                "_id": "8434059834590834590834fa",
                "userId": "345903459034594355cea11e",
                "userName": "bar"
            }
        ]
    }
]

Then the routine to parse it might look like:

func loadPosts(postsJSON: NSArray) {
    var posts = [Post]()

    for postDictionary in postsJSON {
        let post = Post()
        let createDateString = postDictionary["createDate"] as String
        post.message = postDictionary["message"] as String
        post.identifier = postDictionary["_id"] as String
        post.createDate = createDateString.rfc3339Date()

        if let authorsArray = postDictionary["author"] as NSArray? {
            var authors = [Author]()
            for authorDictionary in authorsArray {
                let author = Author()
                author.userId = authorDictionary["userId"] as String
                author.userName = authorDictionary["userName"] as String
                author.identifier = authorDictionary["_id"] as String
                authors.append(author)
            }
            post.authors = authors
        }

        posts.append(post)
    }

    // obviously, do something with `posts` array here, either setting some class var, return it, whatever
}

And this is my conversion routine from String to NSDate:

extension String {

    /// Get NSDate from RFC 3339/ISO 8601 string representation of the date.
    ///
    /// For more information, see:
    ///
    /// https://developer.apple.com/library/ios/qa/qa1480/_index.html
    ///
    /// :returns: Return date from RFC 3339 string representation

    func rfc3339Date() -> NSDate? {
        let formatter = NSDateFormatter()

        formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZ"
        formatter.timeZone = NSTimeZone(forSecondsFromGMT: 0)
        formatter.locale = NSLocale(localeIdentifier: "en_US_POSIX")

        return formatter.dateFromString(self)
    }
}