Error: Couldn't decode data array

Using Swift
1

from this public postman mock server https://fb76208c-d403-4f0e-94fe-1b57cf284a4c.mock.pstmn.io/relays

you will receive this json reply { "relays": [ { "room": "Office", "state": "Off", "bcm": "2" }, { "room": "Garage", "state": "Off", "bcm": "3" }, { "room": "UpStairs", "state": "Off", "bcm": "4" }, { "room": "Master", "state": "Off", "bcm": "17" }, { "room": "MasterBath", "state": "Off", "bcm": "27" }, { "room": "FrontDoor", "state": "Off", "bcm": "15" }, { "room": "LargeBedroom", "state": "Off", "bcm": "18" }, { "room": "SmallBedroom", "state": "Off", "bcm": "22" }, { "room": "Kitchen", "state": "Off", "bcm": "24" }, { "room": "Playroom", "state": "Off", "bcm": "10" }, { "room": "Outside", "state": "Off", "bcm": "9" }, { "room": "Laundry", "state": "Off", "bcm": "25" }, { "room": "Hexroom", "state": "Off", "bcm": "5" }, { "room": "Empty1", "state": "Off", "bcm": "6" }, { "room": "Empty2", "state": "Off", "bcm": "13" }, { "room": "Empty3", "state": "Off", "bcm": "19" } ] }

playground code below fails to decode. what I'm I doing wrong?

struct switchState: Decodable {
let room: String
let state: String
let bcm: String
}

struct piOutput: Decodable {
let relays: switchState // set outer key relays
}

import UIKit

let url = URL(string: "https://fb76208c-d403-4f0e-94fe-1b57cf284a4c.mock.pstmn.io/relays")!

let task = URLSession.shared.dataTask(with: url) { data, response, error in
    
  // ensure there is no error for this HTTP response
  guard error == nil else {
    print ("error: \(error!)")
    return
  }
    
  // ensure there is data returned from this HTTP response
  guard let data = data else {
    print("No data")
    return
  }
    
  // Parse JSON into array of Car struct using JSONDecoder
    guard let relays = try? JSONDecoder().decode([piOutput].self, from: data) else {
    print("Error: Couldn't decode data array")
    return
  }
    
    for switches in relays {
    print("switch state is \(switches.relays.room)")
    print("room name is \(switches.relays.room)")
    print(relays)

}
}

// execute the HTTP request
task.resume()
2

A. Your JSON is a dictionary with one key ("relays"), whose value is an array of switchState.

B. You've decoded an array of dictionaries, each with a single switchState.

A != B