类型 '()' 不能符合 'View'； 只有 struct / enum / class 类型可以符合协议

Question

Hi I'm trying to make some changes in my app, but I can't because whenever I try to add a func in my View I get the following error: "Type '()' cannot conform to 'View'; only struct / enum / class types can conform to protocols "

Image

What my func does:

  func regiterUserAppleBlog(uid:String,completion :@escaping (Bool) -> (Void)) {

    var isExist = false
    COLLECTION_USRES.whereField("uid", isEqualTo: uid).getDocuments { snapshot, _ in

        if (snapshot?.documents.count)! > 0 {
            isExist = true
            print("User exists")
        }
        completion(isExist)
        
    }
}

It is looking in my console if the user's document exists.

and I am implementing it in that View because I want it to tell me if the doc exists or if not, if it does not exist I send it to create the doc and if it exists I send it to the MainTabView.

Code:

struct ContentView: View {
@EnvironmentObject var viewModel: AuthViewModel

@State var registerUser: Bool = false

@State var selectedIndex = 0


var body: some View {
  
    Group {
        if viewModel.userSession == nil {
            AppPreview()
        } else {

            regiterUserAppleBlog(uid: ACFF.UID ?? "") { (isExist) -> (Void) in
                if !isExist {
                    print("User exists")
                   if let user = viewModel.currentUser {
                MainTabView(user: user, selectIndex: $selectedIndex)
                   }
                } else {
                    print("User missing")
                }
            }

        }
    }
    
}

func regiterUserAppleBlog(uid:String,completion :@escaping (Bool) -> (Void)) {

    var isExist = false
    COLLECTION_USRES.whereField("uid", isEqualTo: uid).getDocuments { snapshot, _ in

        if (snapshot?.documents.count)! > 0 {
            isExist = true
            print("User exists")
        }
        completion(isExist)
        
    }
}}

If someone can help me it would be very helpful, thanks.

Answer 1

You can't make function calls inside SwiftUI view builders. You can only do it in response to some events.

And actually you need to made such calls inside your view model, and inside your view just display different views depending on view state

You can place your register logic inside didSet , so it'll be called once session is established.

struct ContentView: View {
    
    @EnvironmentObject var viewModel: AuthViewModel

    @State var registerUser: Bool = false

    @State var selectedIndex = 0
    var body: some View {
        Group {
            if let user = viewModel.currentUser {
                MainTabView(user: user, selectIndex: $selectedIndex)
            } else if viewModel.userSession == nil {
                AppPreview()
            } else {
                // display something while registering on leave empty
            }
        }
    }
}

class AuthViewModel: ObservableObject {
    @Published
    var userSession: Session? {
        didSet {
            if userSession != nil {
                register()
            }
        }
    }
    
    @Published
    var currentUser: User?
    
    func register() {
        if userSession != nil && currentUser == nil {
            regiterUserAppleBlog(uid: ACFF.UID ?? "") { (isExist) -> (Void) in
                if !isExist {
                    print("User exists")
                } else {
                    print("User missing")
                }
            }
        }
    }
}