CODEWITHSUNDEEP
jsonswiftdecodable
Case Silva
Case Silva

Reputation: 514

How to use JSONDecoder with multiple possible data structures

I am parsing a feed of json data representing events. On a day where there ARE events, the json feed will be a Dictionary of Dictionaries, and looks something like this:

{
    "19374176" : 
    {
        "event_title" : "Cool Fun Thing to Do",
        "event_description" : "Have fun and do something cool",
        "event_start_time" : "13:00:00",
        "event_end_time" : "14:00:00"
    },
    "90485761634" :
    {
        "event_title" : "Nap Time",
        "event_description" : "Lay down and go to sleep.",
        "event_start_time" : "15:00:00",
        "event_end_time" : "16:00:00"
    }
}

I have a structure set up and I can decode and use this information the way I would like to currently with this code that is part of a larger function:

URLSession.shared.dataTask(with: url){(data, response, error) in
        if error != nil {
            print("session error: ", error!.localizedDescription)
        }

        guard let data = data else { return }

        do {
            let decoder = JSONDecoder()
            decoder.keyDecodingStrategy = .convertFromSnakeCase
            print(data)
            var eventData = try decoder.decode([String:Event].self, from: data)

            DispatchQueue.main.async{
                self.events = Array(eventData.values).sorted(by: {$0.timeStart < $1.timeStart
                })

                self.updateView()
                self.refreshControl.endRefreshing()
                self.activityIndicatorView.stopAnimating()
            }
        } catch DecodingError.typeMismatch(let type, let context){
            //No Dictionary of Events in Data
            print("key:", type, "context: ", context)
        } catch let jsonError{
            print("json error: ", jsonError)
        }
    }.resume()
}

My issue right now is that, on days where there no events, the json feed is an empty Array:

[]

This causes a type mismatch which I handle, but if I try to call the updateView, refreshControl, or activityIndicatorView's functions from the catch, I get an error that I cannot call them outside the main thread.

I tried to do nested try blocks to assign the eventData variable (first to see if it is an [String] ((empty array, no events)) and then to [String:Any] ((array with values of events))), but that gave me an error for the URLSession.

Is there a better approach to this to see if the json is an empty array vs a populated dictionary of my Event values and update the views regardless?

Upvotes: 1

Views: 70

Answers (1)

Shehata Gamal
Shehata Gamal

Reputation: 100503

Try refreshing them outside of any blocks 

do { 
    let decoder = JSONDecoder()
    decoder.keyDecodingStrategy = .convertFromSnakeCase
    print(data)
    var eventData = try decoder.decode([String:Event].self, from: data)
    self.events = Array(eventData.values).sorted(by: {$0.timeStart < $1.timeStart

} catch DecodingError.typeMismatch(let type, let context){
    //No Dictionary of Events in Data
    print("key:", type, "context: ", context)
} catch let jsonError{
    print("json error: ", jsonError)
}

DispatchQueue.main.async{
    self.updateView()
    self.refreshControl.endRefreshing()
    self.activityIndicatorView.stopAnimating()
}

Upvotes: 3

Related Questions