Child Objects

A user can create posts within a site. That user might be the creator of the blog, or it might be a different user. A Post fact refers to the Site parent, the author User, and also includes a timestamp to differentiate it from other posts.

[FactType("Blog.Post")]
public record Post(Site site, User author, DateTime createdAt) { }

Renderer.RenderTypes(typeof(Post))

var post0 = await jinagaClient.Fact(new Post(site, user, DateTime.UtcNow));
var post1 = await jinagaClient.Fact(new Post(site, user, DateTime.UtcNow));

jinagaClient.RenderFacts(post0, post1)

When using the application, you will first select a site from the list. Then you will navigate to a page where you see the posts. The specification should therefore start from the site.

var postsInSite = Given<Site>.Match((site, facts) =>
    from post in facts.OfType<Post>()
    where post.site == site
    select post);

var posts = await jinagaClient.Query(postsInSite, site);

posts.Count()

Continue the pattern to define deletion, restoration, and mutable properties for the child objects.

[FactType("Blog.Post.Title")]
public record PostTitle(Post post, string value, PostTitle[] prior) { }

[FactType("Blog.Post.Content")]
public record PostContent(Post post, string markdown, PostContent[] prior) { }

[FactType("Blog.Post.Deleted")]
public record PostDeleted(Post post, DateTime deletedAt) { }

[FactType("Blog.Post.Restored")]
public record PostRestored(PostDeleted deleted) { }

Renderer.RenderTypes(
    typeof(PostTitle),
    typeof(PostContent),
    typeof(PostDeleted),
    typeof(PostRestored))

var postTitle0 = await jinagaClient.Fact(new PostTitle(
    post0, "Welcome to My Blog", []));
var postContent0 = await jinagaClient.Fact(new PostContent(
    post0, "This is my first post.", []));

var postTitle1 = await jinagaClient.Fact(new PostTitle(
    post1, "Interesting Facts", []));
var postContent1 = await jinagaClient.Fact(new PostContent(
    post1, "Let me tell you about this thing that I love.", []));

var post0Deleted = await jinagaClient.Fact(new PostDeleted(
    post0, DateTime.UtcNow));

jinagaClient.RenderFacts(
    postTitle0,
    postContent0,
    postTitle1,
    postContent1,
    post0Deleted)

Extend the specification to filter out deleted posts and project properties such as title.

var postsInSite = Given<Site>.Match((site, facts) =>
    from post in facts.OfType<Post>()
    where post.site == site
    where !facts.Any<PostDeleted>(pd => pd.post == post &&
        !facts.Any<PostRestored>(pr => pr.deleted == pd))
    select new
    {
        Post = post,
        Title =
            from title in facts.OfType<PostTitle>()
            where title.post == post
            where !facts.Any<PostTitle>(next => next.prior.Contains(title))
            select title.value,
        Content =
            from content in facts.OfType<PostContent>()
            where content.post == post
            where !facts.Any<PostContent>(next => next.prior.Contains(content))
            select content.markdown
    });

var posts = await jinagaClient.Query(postsInSite, site);

posts

index value

{ Post = Post { ... }, Title = [ Interesting Facts ], Content = [ Let me ... ] }

Post

Post { site = Site { ... }, author = Jinaga.User, createdAt = 5/18/2024 5:54:09 PM }

site

Site { creator = Jinaga.User, createdAt = 5/18/2024 5:54:05 PM }

creator

Jinaga.User

publicKey	--- FAKE USER ---

createdAt 2024-05-18 17:54:05Z

author

Jinaga.User

publicKey	--- FAKE USER ---

createdAt 2024-05-18 17:54:09Z

Title

[ Interesting Facts ]

(values)	[ Interesting Facts ]

Content

[ Let me tell you about this thing that I love. ]

(values)	[ Let me tell you about this thing that I love. ]

Create a view model for the child screen in the same way you did for the parent.

var postsViewModel = posts.Select(p => new
{
    Title = p.Title.FirstOrDefault() ?? "New post",
    Content = p.Content.FirstOrDefault() ?? ""
});

postsViewModel

index value

{ Title = Interesting Facts, Content = Let me ... }

Title	Interesting Facts
Content	Let me tell you about this thing that I love.

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