For example, how do I display the descriptors for each record in a list, such as:

• NUTTY, FRUITY
• FATTY
• FRUITY

(Note that I made descriptors optional in my model because the array might be empty)

Here is my JSON file code from file named flavors.json:

[
    {
        "id": "U45773",
        "flavorGroup": "CASHEW",
        "name": "NATURAL CASHEW FLAVORING",
        "isBeer": true,
        "isSeltzer": true,
        "isNatural": true,
        "descriptors": ["NUTTY", "FRUITY"],
        "keywords": ["aromatic", "fattt-buttery", "brown", "nutty", "roasted", "creamy"]
    },
    {
        "id": "U63639",
        "flavorGroup": "BLACK WALNUT",
        "name": "NATURAL AND ARTIFICIAL WALNUT FLAVOR",
        "isBeer": true,
        "isSeltzer": false,
        "isNatural": true,
        "descriptors": ["FATTY"],
        "keywords": ["sweet", "molasses", "woody", "slight dried fruit (amber ale)"]
    },
    {
        "id": "562811",
        "flavorGroup": "APRICOT",
        "name": "NATURAL AND ARTIFICIAL APRICOT FLAVOR",
        "isBeer": true,
        "isSeltzer": false,
        "isNatural": true,
        "descriptors": ["FRUITY"],
        "keywords": ["juicy", "skunky", "peach", "floral", "slight green (sierra nevada pale ale)"]
    }
]

Here is my model code:

struct Flavor: Codable, Identifiable {
    enum CodingKeys: CodingKey {
        case id
        case flavorGroup
        case name
        case isBeer
        case isSeltzer
        case isNatural
        case descriptors
        case keywords
    }
    let id, flavorGroup, name: String
    let isBeer, isSeltzer, isNatural: Bool
    let descriptors, keywords: [String]?
}

Here is my view model code:

class ReadData: ObservableObject  {
    @Published var flavors = [Flavor]()
    init(){
        loadData()
    }
    func loadData()  {
        guard let url = Bundle.main.url(forResource: "flavors", withExtension: "json")
            else {
                print("Json file not found")
                return
            }
        let data = try? Data(contentsOf: url)
        let flavors = try? JSONDecoder().decode([Flavor].self, from: data!)
        self.flavors = flavors!   
    }    
}

This is my best attempt at the view code:

struct DescriptorListView: View {
    @ObservedObject var datas = ReadData()
    var body: some View {
        List(datas.flavors) { item in
            ForEach(item.descriptors, id: \.self) { descriptor in
                Text("- \(descriptor)")
            }
        }
    }
}

It produces these compiler errors that I do not understand how to fix:

Value of optional type '[String]?' must be unwrapped to a value of type '[String]'

Coalesce using '??' to provide a default when the optional value contains 'nil'

Force-unwrap using '!' to abort execution if the optional value contains 'nil'

CodePudding user response：

You were very close with your attempt. The major issue is that descriptors is an Optional. That means that you have to somehow unwrap that optional value -- I've used if let, which is a technique called "optional binding".

The other issue is that your current code would list each descriptor on a different line. I've joined the descriptors together using joined instead and presented them on one line.

struct DescriptorListView: View {
    @ObservedObject var datas = ReadData()
    var body: some View {
        List(datas.flavors) { item in
            HStack {
                if let descriptors = item.descriptors {
                    Text(descriptors.joined(separator: ", "))
                } else {
                    Text("(no data)")
                }
            }
        }
    }
}