Setup example data in SwiftUI Previews

[NoahKamara]

I have a view that dynamically fetches items, and I want to preview it by injecting data into the database in prepareDependencies. However, the injected data doesn’t appear because the operations execute in the wrong order.

In my example, the database is accessed before it is prepared, so any modifications made during preparation are not reflected in the view.

🟣 Dependencies/DependencyValues.swift:286: Ignoring dependencies prepared in preview app entry point
🟣 Dependencies/DependencyValues.swift:583: A blank, in-memory database is being used. ...
Items Optional(1)
🟣 SharingGRDB/DefaultDatabase.swift:42: @Dependency(\.defaultDatabase) has already been accessed or prepared ....
PREPARED
START QUERY
UPDATED QUERY 0

struct ExampleView: View {
    @State.SharedReader(value: [])
    var items: [Item]
    
    @State
    var showHidden: Bool = true
    
    var body: some View {
        Text(items.count, format: .number)
        Toggle("Show Hidden", isOn: $showHidden)
            .task(id: [showHidden] as [AnyHashable]) {
                do {
                    print("START QUERY")
                    try await $items.load(.fetchAll(sql: "SELECT * FROM item"))
                    print("UPDATED QUERY", items.count)
                } catch {
                    print("Updating failed", error)
                }
            }
    }
}

#Preview {
    let _ = prepareDependencies {
        let database: DatabaseWriter = .appDatabase
        
        
        try! database.write { db in
            let item = Item(
                id: .init(),
                url: URL.downloadsDirectory.appending(
                    component: "image.png"
                ),
                type: .png
            )
            
            try item.insert(db)
        }
        
        let items = try? database.read { db in
            try Item.all().fetchAll(db)
        }
        print("Items", items?.count)
        
        $0.defaultDatabase = database
        print("PREPARED")
    }
    
    ExampleView()
}

[mbrandonw]

Hi @NoahKamara, I think you need to track down a dependency is being accessed before prepare. Can you provide a small project that demonstrates the problem you are having?