尝试将AlamoFire JSON响应映射到类并收到“致命错误：在展开可选包时意外发现nil”

Question

I am using AlamoFire to pull my API to populate the cells of my tableView. The app is able to Build, but crashes soon after with the customary "Fatal Error: unexpectedly found nil while unwrapping an Optional value." I've gone over all my optional values and can't figure out which one is causing the problem. Xcode says the problem comes during the .map portion of AlamoFire. Any help would be appreciated.

Before I get to the code, one of the values in my JSON is null for every key (I didn't write the JSON). It's not "null", just null. Could this be causing the problem even though I'm not mapping that key to my Class?

The JSON is an Array of Dictionaries. After making the .GET request, I'm taking the JSON response and mapping it to a variable that I initialized as an Array of Class types.

Here is the code:

var users = [User]()  //User is the class I created  
var results = NSMutableOrderedSet()    
let url = "http://www.example.com"
let appToken = "abcd12345"


Alamofire.request(.GET, url, parameters: ["appToken": appToken]).responseJSON() {
        (_, _, JSON, _) in
        let users = (JSON!.valueForKey("results") as! [NSDictionary]).map {
            User(name: $0["username"] as! String, image: $0["profileImage"] as! String, email: $0["email"] as! String, lat: $0[("lat" as NSString).doubleValue] as! Double, lon: $0[("lon" as NSString).doubleValue] as! Double, distance: $0["status"] as! Int)
        }

        self.results.addObjectsFromArray(users)
        self.localTableView!.reloadData()

    }

And here is the Class type from my User.swift:

class User: NSObject, MKAnnotation {
var name:String!
var profileImage:String!
var email:String!
var lat:Double
var lon:Double
var distance:Int!

var coordinate: CLLocationCoordinate2D
var title: String
var subtitle: String
var imageName: String

var userID:String!
var firstName: String!
var lastName: String!

init(name:String, image:String, email:String, lat:Double, lon:Double, distance:Int){
    self.name = name
    self.profileImage = image
    self.email = email
    self.lat = lat
    self.lon = lon
    self.distance = distance

    self.coordinate = CLLocationCoordinate2DMake(lat, lon)
    self.title = name
    self.subtitle = twitterName
    self.imageName = "image.png"


}

I've read in some help sections that I might not be initializing the instance of my class correctly, but I've tried every combination to no avail. I've also tried playing with NSMutableDictionary, but that didn't fix anything.

Answer 1

Thank you everyone for your responses. They were all very helpful.

I shortened parts of my code to the essentials when I shared it above, but the problem was found in mapping the var lat and var lon to my user array. In the API they were doubles, but were put in quotation marks, so it was reading it as a String. I had realized the problem and wrote code to convert them from Strings to Doubles. However, I put that in the .map{} portion of my code (not seen above). There may be a way to do this there, but it never worked for me.

Instead, I found my solution by changing my class User to make these changes as follows:

let lat: String
let lon: String

var latDouble: Double
var lonDouble: Double

And then initialized it as follows:

self.latDouble = (lat as NSString).doubleValue
self.lonDouble = (lon as NSString).doubleValue

I also incorporated SwiftyJSON to retrieve my API data and then filled my array as follows:

Alamofire.request(.GET, url, parameters: ["appToken": appToken]).responseJSON(){
        (_,_,json,_) in
        if (json != nil){
            var jsonObj = JSON(json!)

            if let userArray = jsonObj ["results"].array {

                for userDict in userArray {
                    var name: String! = userDict["username"].string
                    var email: String! = userDict["email"].string
                    var image: String! = userDict["profileImage"].string
                    var lat: String! = userDict["lat"].string
                    var lon: String! = userDict["lon"].string
                    var distance: Int! = userDict["status"].int

                    var user = User(name: name, image: image, email: email,  lat: lat, lon: lon, distance: distance)

                    self.users.append(user)
                }

                self.localTableView.reloadData()
            }

I realize this might not be the best or only solution, but it solved my problem. I hope this might be helpful to someone else. Thanks again.

Answer 2

There are tons of optionally getting unwrapped in your callback and any of them could be nil. You need to get in the debugger and inspect the JSON that came back. If you have difficulty with the debugger you could print() the JSON variable before trying to use it and see the contents.

A tip: don't use implicitly unwrapped optional types on your class properties. It's not a safe practice. If you aren't going to modify a property after creating the class instance, use let name: String for instance instead of var name: String!. Let the compiler help you write a correct program.