Retrieving the param from the previous ViewModel

In the PostDetailViewModel, we need to get the param from the IMvxNavigationService. Change the basic class of the PostDetailViewModel like this:

public class PostDetailViewModel : MvxViewModel

Now it has a generic type constraint to receive the param. To do this, we need to update the Prepare override method, which is the right place to receive the param that is passed by the previous ViewModel. Add a private variable to store the post id:

private int _postId;

Create a new object to store the comments:

#region CommentList;
private MvxObservableCollection<Comment> _commentList;
public MvxObservableCollection<Comment> CommentList
{
get => _commentList;
set => SetProperty(ref _commentList, value);
}
#endregion

And update the Prepare method to initialize the variables like this:

public override void Prepare(Post post)
{
// This is the first method to be called after construction
CommentList = new MvxObservableCollection<Comment>();
_postId = post.Id;
}

After that, we can use the _postId variable in the Initialize method to load the data from the APIs, as shown below:

public override async Task Initialize()
{
// Async initialization, YEY!
await base.Initialize();
await GetPost(_postId);
await GetComments(_postId);
}

Here is the result of the Android project:

For the UWP project:

Let us get deep into the IMvxNavigationService in the next section.