SwiftUI Preview canvas and Core Data

Question

Preview canvas is is crashing but in simulator everything working fine. I assuming it related to @ObservedObject and @Fetchrequest...

tried solution for here Preview

Answer 1

This is my solution.

I don't want use CoreData in view. I want MVVM style. So you need to mock Core data for display in Canvas view.

This is an example :

// View
struct MyView: View {
    @ObservedObject var viewModel: PreviewViewModel
}

// View Model
final class MyViewModel: ObservableObject {
   @Published var repository: RepositoryProtocol // CoreData
}

// Repository
protocol RepositoryProtocol { }
class Repository: RepositoryProtocol { ... } 
class MockRepository: RepositoryProtocol { ... } // Create a Mock


// Init of your view
// If Canvas use mock
if ProcessInfo.processInfo.environment["XCODE_RUNNING_FOR_PREVIEWS"] == "1" {
    repository = MockRepository() 
    
// else App use Repository
} else {
    repository = Repository.shared
}

let viewModel = MyViewModel(repository:repository)
MyViewModel(viewModel: viewModel)