How do use SwiftUI to decode nested JSON elements and show the information in a view?

Question

I am able to show the name, cost per launch, etc of the JSON. However I cannot access the value for payload_weights and flic_images. I think because they are inside an array of objects.

Here is part of the JSON file

[
  {
    "rocketid": 1,
    "id": "falcon1",
    "name": "Falcon 1",
    "type": "rocket",
    "active": false,
    "stages": 2,
    "boosters": 0,
    "cost_per_launch": 6700000,
    "success_rate_pct": 40,
    "first_flight": "2006-03-24",
    "country": "Republic of the Marshall Islands",
    "company": "SpaceX",
    "height": {
      "meters": 22.25,
      "feet": 73
    },
    "diameter": {
      "meters": 1.68,
      "feet": 5.5
    },
    "mass": {
      "kg": 30146,
      "lb": 66460
    },
    "payload_weights": [
      {
        "id": "leo",
        "name": "Low Earth Orbit",
        "kg": 450,
        "lb": 992
      }
    ]

This is my model:

struct Rocket: Codable, Identifiable {
    var id: String
    var name: String
    var type: String
    var active: Bool
    var stages: Int
    var boosters: Int
    var cost_per_launch: Int
    
    struct PayloadWeight: Codable {
        var id: String
        var name: String
        var kg: Int
        var lb: Int
    }
    
    var payload_weights: [PayloadWeight]
}

This is the view I want to show my data.

struct ContentView: View {
    let rockets = Bundle.main.decode([Rocket].self, from: "Rocket.json")
   
    var body: some View {
        List(rockets) { rocket in
            HStack {
                Text(rocket.name)
            }
        }
    }
}

pawello2222 · Accepted Answer · 2020-07-26 22:01:01Z

1

The payload_weights property is an array. Which means you can either access the first item (if it exists) or display all of them.

You may try the following:

struct ContentView: View {
    let rockets: [Rocket] = Bundle.main.decode([Rocket].self, from: "Rocket.json")
   
    var body: some View {
        List(rockets) { rocket in
            VStack {
                Text(rocket.name)
                List(rocket.payload_weights) { payloadWeight in
                    self.payloadWeightView(payloadWeight: payloadWeight)
                }
            }
        }
    }
    
    func payloadWeightView(payloadWeight: Rocket.PayloadWeight) -> some View {
        Text(payloadWeight.name)
    }
}

Note: you need to conform PayloadWeight to Identifiable as well:

struct PayloadWeight: Codable, Identifiable { ... }

answered Jul 26, 2020 at 22:01

pawello2222

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