swift3 - Parsing JSON using Swift 3

Question

I have this json data that I want to consume in Swift 3. I'm learning Swift and building a very basic app that displays the list of items in tableUIView from JSON.

{
  "expertPainPanels" : [
     {
       "name": "User A",
       "organization": "Company A"
     },
     {
       "name": "User B",
       "organization": "Company B"
     }
    ]
}

I'm trying to get this data using Swift 3.

if (statusCode == 200) {
    do{
        let json = try? JSONSerialization.jsonObject(with: data!, options:.allowFragments) // [[String:AnyObject]]

/*
    If I do this: 

    let json = try? JSONSerialization.jsonObject(with: data!, options:.allowFragments) as! [String:Any]

    if let experts = json?["expertPainPanels"] as! [String: Any] {
    I get "Initializer for conditional binding must have Optional type, not '[String: Any]'"

*/


        // Type 'Any' has no subscript members.
        if let experts = json["expertPainPanels"] as? [String: AnyObject] {

            for expert in experts {
                let name = expert["name"] as? String
                let organization = expert["organization"] as? String
                let expertPainPanel = ExpertPainPanel(name: name, organization: organization)!
                self.expertPainPanels += [expertPainPanel]
                self.tableView.reloadData()
                self.removeLoadingScreen()
            }
        }
     }catch {
          print("Error with Json: (error)")
        }
     }

It was working fine in Swift 2. I updated to Swift 3 which broke the code. I read several SO, but I still have hard time understanding it. I applied some suggestions including JSON Parsing in Swift 3, but I'm still unable to fix the error I'm getting.

Answer 1

As of Swift 3, you need to do a cast early on.

This line:

let json = try? JSONSerialization.jsonObject(with: data!, options:.allowFragments)

Should become this:

let json = try JSONSerialization.jsonObject(with: data!, options:.allowFragments) as? [String : AnyObject]

This is because JSONSerialization now returns Any, which does not implement a variation for the [] operator. Make sure you safely unwrap the cast and take the common measures to ensure you don't crash your program.

Edit: Your code should more or less look like this.

let data = Data()
let json = try JSONSerialization.jsonObject(with: data, options:.allowFragments) as! [String : AnyObject]
if let experts = json["expertPainPanels"] as? [String: AnyObject] {