Parsing data with Decodeable swift 4.0 not reading data - Xcode

Question

Im trying to parse data with JSONDecoder, however I keep getting an error. I am unsure why? If anyone could have a look at the code and explain whats going wrong, it would be greatly appreciated!

struct Stops1 : Decodable{
let StopName : String
let StopLat : String
let StopLon: String
}


 let path = Bundle.main.path(forResource: "newStops", ofType: "json")
 let url = URL(fileURLWithPath: path!)

    do {
        let data = try Data(contentsOf: url)
        let Stops = try JSONDecoder().decode([Stops1].self, from: data)
        print(Stops)

    }
    catch let jsonErr {
        print("Error occured during Parsing", jsonErr)
    }

below is the local json file called "newStops" :

  {
  "Stops1" : {

    {
        "StopName": "loc 1",
        "StopLat": "-46.450364",
        "StopLon": "169.659519"
    },
    {
        "StopName": "loc 2",
        "StopLat": "-45.898395",
        "StopLon": "170.486386"
    },
    {
        "StopName": "loc 3",
        "StopLat": "-36.635997",
        "StopLon": "174.747697"
    },
  }
}

vadian · Accepted Answer · 2018-03-11 10:02:36Z

1

The JSON is invalid.

I guess the value for key Stops1 is supposed to be an array, then the JSON must be

{
 "Stops1" : [ {...},  {...},  {...} ] 
}

Some general thoughts about the JSON and the associated struct

According to the naming convention it's recommended to name the keys lowercased
The name of the struct should be in singular form (Stop)
To include the name of the struct also in the properties runs contrary to the naming philosophy of Swift.

I recommend this simple form of the JSON

{
    "stops" : [
        {"name": "loc 1", "lat": "-46.450364", "lon": "169.659519"},
        {"name": "loc 2", "lat": "-45.898395", "lon": "170.486386"},
        {"name": "loc 3", "lat": "-36.635997", "lon": "174.747697"}
    ]
}

and the associated struct

struct Stop : Decodable {
    let name : String
    let lat : String
    let lon: String
}

The root object is a dictionary with key stops, this requires an extra umbrella struct:

struct Root : Decodable {
    let stops : [Stop]
}

Now decode the JSON

let url = Bundle.main.url(forResource: "newStops", withExtension: "json")!

do {
    let data = try Data(contentsOf: url)
    let root = try JSONDecoder().decode(Root.self, from: data)
    for stop in root.stops {
       print(stop.name)
    }
}
catch {
    print("Error occured during Parsing", error)
}

edited Mar 11, 2018 at 10:02

answered Mar 11, 2018 at 9:23

vadian

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2 Comments

DashCode17 Over a year ago

How can I call all ''name" values with this method?

DashCode17 Over a year ago

Thank you so much for you help! :)

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