ForEach over an array of protocol implementations?

Question

I'm starting to learn SwiftUI, and so I decided to write a simple password manager as a learning exercise. I've defined a protocol with the common attributes in my passwords:

protocol Secret: Codable {
    
    var id: String { get set }
    var name: String { get set }
    var createdDate: Date { get set }
    
    var favorite: Bool { get set }
    
    var category: SecretCategory { get set }
    
    var notes: String { get set }
    
    init(_ id: String, name: String)
    init(_ id: String, name: String, favorite: Bool)

}

Then, I've defined a couple of Swift struct s that implement this protocol and define the properties of various types of secrets:

struct LoginSecret: Secret, Identifiable {
    
    var id: String
    var name: String
    var createdDate: Date = Date()
    
    var favorite: Bool = false
    
    var category: SecretCategory = .login
    
    var notes: String = ""
    
    var username: String = ""
    var encryptedPassword: String = ""
    
    var websiteURLs: [String] = []
    
    init(_ id: String, name: String) {
        self.id = id
        self.name = name
    }
    
    init(_ id: String, name: String, favorite: Bool) {
        self.id = id
        self.name = name
        self.favorite = favorite
    }
}

...and...

struct BankAccountSecret: Secret, Identifiable {
    
    var id: String
    var name: String
    var createdDate: Date = Date()
    
    var favorite: Bool = false
    
    var category: SecretCategory = .bankAccounts
    
    var notes: String = ""
    
    var bankName: String = ""
    var nameOnAccount: String = ""
    var routingNumber: String = ""
    var accountNumber: String = ""
    
    var swift: String = ""
    var iban: String = ""
    
    var encryptedPIN: String = ""
    
    var branchPhoneNumber: String = ""
    var branchAddress: Address = Address()
    
    init(_ id: String, name: String) {
        self.id = id
        self.name = name
    }
    
    init(_ id: String, name: String, favorite: Bool) {
        self.id = id
        self.name = name
        self.favorite = favorite
    }
}

These work just fine, and I'm able to Encode/Decode values in JSON for display later. However, now I'm working on my SwiftUI code. I want to display each item in a List , iterating over an Array of Secret objects using SwiftUI's ForEach . My code looks like this:

struct SecretsListView: View {

    @State    
    var secrets: [Secret]
    
    var body: some View {
        NavigationView {
            List {
               ForEach(secrets) { secret in
                  <snip>
               }
            }
        }
   }
}

However, when I compile I get an error saying...

Value of protocol type 'Secret' cannot conform to 'Identifiable'; only struct/enum/class types can conform to protocols

Is there no way to iterate over an array of Secret objects? Is there a different way to accomplish this? Is this issue specific to SwiftUI's ForEach ? Should I use the standard Swift Array forEach method instead? Any guidance you can provide is greatly appreciated. I've worked with Swift and UIKit for a while, but SwiftUI is new and I want to make sure I'm developing for the framework correctly.

Answer 1

Yes, only SwiftUI.ForEach requires the Identifiable conformance, Array.forEach does not require it.

There are several other initialisers of ForEach though that don't require your model type to conform to Identifiable .

You could use init(_ data: Data, id: KeyPath<Data.Element, ID>, content: @escaping (Data.Element) -> Content) for instance (assuming that ID conforms to Hashable , which Secret.id does, since it's a String ).

ForEach(secrets, id: \.id) { secret in
    <snip>
}

Another solution would be passing the indices of the array to ForEach , then you could use ForEach(secrets.indices) , but since you have a Hashable property on Secret that you can use as the id , that's a the previous one is a better solution.