How to Json decode API data with an array?

Question

I am learning Swift and trying to get elevation data based on coordinates from the Open Elevation API.

I found a code to make the request and decode the data using structs.

My problem is that the API result includes the information in an array:

{"results": [{"latitude": 41.161758, "longitude": -8.583933, "elevation": 117}]}

What I have been able to program so far does save the data as an array in json.results, but only with one index including all of the data:

[API.MyResult(latitude: 41.16176, longitude: -8.583933, elevation: 117)]

("API" is the name of the file)

Here is my code:

import UIKit

class ViewController: UIViewController {

    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        
        
        let url = "https://api.open-elevation.com/api/v1/lookup?locations=41.161758,-8.583933"
        
        getData(from: url)
        
    }

    
    
    
    private func getData(from url: String){
        
        let task = URLSession.shared.dataTask(with: URL(string: url)!, completionHandler: {data, response, error in
            
            guard let data = data, error == nil else {
                print("error")
                return
            }
            
            var result: Response?
            //print(result)
            
            
            
            do{
                result = try JSONDecoder().decode(Response.self, from: data)
            }
            catch{
                print(error.localizedDescription)
            }
            
            
            guard let json = result else {
                return
            }
        
            
            
            print(json.results)
            
            //print(json.results.latitude)
            //print(json.results.longitude)
            //print(json.results.elevation)
            
            
        })
        task.resume()
    }
    
    
    
}
    



struct Response: Codable {
    let results: [MyResult]
}
    
struct MyResult: Codable {
    let latitude: Float
    let longitude: Float
    let elevation: Int
}

Trying to print out json.results.latitude leads to the error

"Value of type '[MyResult]' has no member 'latitude'"

I assume at some point, a variable has to be defined as an array.

What needs to be changed here?

Answer 1

result is indeed a single object, but the property results is an array (multiple objects).

A slightly different naming avoids the confusion.

Notes:

• Never print literal "error" or error.localizedDescription in a Decoding context, always print the error instance.

• Proceed to parse the result in the do scope

    private func getData(from url: String){
        guard let url = URL(string: url) else { print("Bad URL", url); return }
        let task = URLSession.shared.dataTask(with: url) {data, _, error in
            if let error = error { print(error); return }
            do {
                let response = try JSONDecoder().decode(Response.self, from: data!)
                for result in response.results {
                    print(result.latitude)
                    print(result.longitude)
                    print(result.elevation)
                }
            }
            catch {
                print(error)
            }
        }
        task.resume()
    }