/// <summary>
/// Returns an existing lifecycle-aware <typeparamref name="TViewModel"/> instance by <paramref name="key"/> if it is presented in the <paramref name="store"/>,
/// or creates a new one using the <paramref name="factory"/> with restoring its <paramref name="state"/>.
/// </summary>
/// <typeparam name="TViewModel">The type of the view model to get.</typeparam>
/// <param name="store">The view model store.</param>
/// <param name="key">The view model unique key.</param>
/// <param name="factory">The view model factory.</param>
/// <param name="state">The view model state bundle.</param>
/// <param name="created"><see langword="true"/> if the view model is created by the <paramref name="factory"/>; otherwise, <see langword="false"/>.</param>
/// <returns>The view model instance.</returns>
/// <exception cref="ArgumentNullException"><paramref name="store"/> or <paramref name="key"/> or <paramref name="factory"/> is <see langword="null"/>.</exception>
/// <exception cref="InvalidOperationException">The <paramref name="factory"/> returned <see langword="null"/> value for the <typeparamref name="TViewModel"/>.</exception>
public static TViewModel Get <TViewModel>(
ILifecycleViewModelStore store,
string key,
ILifecycleViewModelFactory factory,
IBundle?state,
out bool created)
where TViewModel : class, ILifecycleViewModel, IStateOwner
{
if (store == null)
{
throw new ArgumentNullException(nameof(store));
}
if (key == null)
{
throw new ArgumentNullException(nameof(key));
}
if (factory == null)
{
throw new ArgumentNullException(nameof(factory));
}
var viewModel = store.Get <TViewModel>(key);
created = false;
if (viewModel == null)
{
viewModel = factory.Create <TViewModel>();
if (viewModel == null)
{
throw new InvalidOperationException(
$"'{TypeFormatter.FormatName(factory.GetType())}.{nameof(ILifecycleViewModelFactory.Create)}' " +
$"returned 'null' value for the '{TypeFormatter.FormatName<TViewModel>()}>' view model.");
}
viewModel.ImportState(state);
store.Add(key, viewModel);
created = true;
}
return(viewModel);
}
/// <summary>
/// Sets the lifecycle-aware view model <paramref name="factory"/> that is used to create a view model instance.
/// </summary>
/// <param name="factory">The view model factory.</param>
/// <exception cref="ArgumentNullException"><paramref name="factory"/> is <see langword="null"/>.</exception>
public static void SetFactory(ILifecycleViewModelFactory factory)
{
_factory = factory ?? throw new ArgumentNullException(nameof(factory));
}
