Load User Data
The top-level view model will typically load data related to the logged-in user.
When the authentication service logs a user in, it makes their User fact available via the UserProvider.
Take a UserProvider as a dependency in the view model.
Define a field to hold onto the UserProvider.Handler.
In the Load method, add a handler to the UserProvider.
The handler returns a function that will be called to clean up.
In the Unload method, remove the handler from the UserProvider.
This will cause the cleanup function to be called.
The cleanup function will also be called when the user logs off.
public partial class SiteListViewModel : ObservableObject, ILifecycleManaged
{
private readonly JinagaClient jinagaClient;
private readonly UserProvider userProvider;
private UserProvider.Handler? handler;
public ObservableCollection<SiteHeaderViewModel> Sites { get; } = new();
public SiteListViewModel(JinagaClient jinagaClient, UserProvider userProvider)
{
this.jinagaClient = jinagaClient;
this.userProvider = userProvider;
}
public void Load()
{
handler = userProvider.AddHandler(user =>
{
var specification = Given<User>.Match((user, facts) =>
// ...
);
var observer = jinagaClient.Watch(specification, user, projection =>
{
// Update the Sites collection
});
return () =>
{
observer.Stop();
observer = null;
Sites.Clear();
};
});
}
public void Unload()
{
userProvider.RemoveHandler(handler);
handler = null;
}
}