Projecting Results
A specification gives you all of the related facts.
But sometimes you want to transform those facts into a different shape.
You can do that with the select method.
const postsInSite = model.given(Site).match(site =>
site.successors(Post, post => post.site)
.select(post => ({
hash: j.hash(post),
createdAt: post.createdAt
}))
);When you select the hash or a field of a fact, the resulting value is immutable.
That's because facts themselves are immutable.
If you want to project something that changes, you can select a sub-specification.
Use the successors method to find related facts, and then select again to shape them.
const postsInSite = model.given(Site).match(site =>
site.successors(Post, post => post.site)
.select(post => ({
hash: j.hash(post),
createdAt: post.createdAt,
titles: post.successors(PostTitle, title => title.post)
.select(title => title.value)
}))
);