SwiftUI App works fine in simulator, but not in preview - swift

Question

I'm trying to get preview working in Xcode. Just a simple test app written in Swift. Grabs rows from a Realm database and lists them.
It works fine when I build/run in the simulator but none of the data shows in the ContentView_Preview.
App in Simulator
App in Preview
Here's the code:
import SwiftUI
import RealmSwift
struct HeaderView: View {
var body: some View {
HStack(alignment: .firstTextBaseline) {
Text("Time Spent").font(.largeTitle)
Text("or waisted...").font(.headline)
}
}
}
struct GroupListView: View {
#ObservedResults(TaskGroup.self) var taskGroups
var body: some View {
NavigationView {
// Nothing from here shows in the preview.. but shows fine in the simulator
List(taskGroups) {
Text("Group: " + $0.name)
}
.navigationTitle("Task Groups (\(taskGroups.count))")
// Grrr
}
}
}
struct FooterView: View {
var body: some View {
HStack {
Text("🤬 Grr.. Preview isn't working.")
Spacer()
Text("Simulator works fine though.")
}
}
}
struct ContentView: View {
var body: some View {
VStack(alignment: .leading) {
HeaderView()
GroupListView()
FooterView()
}
.padding()
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
I've searched for hours and tried various different suggestions. No luck. Any help would be wonderful.

Answer 1

In your preview it's likely that taskGroups is empty. You could verify this by sticking something like
if taskGroups.isEmpty {
Text("test")
}
For your preview you should inject some placeholder content. Depending on how Realm works there may be a mechanism to do this already, or you may need to create an abstraction that allows you to do this.