Plugin for defining relation views with custom schemas and derived queries.

Views allow you to create specialized versions of a relation with:

• Custom field selection (subset of original fields)
• Derived query operations (automatic filtering/restrictions)
• Separate struct modules for type safety

Usage

defmodule MyApp.Users do
  use Drops.Relation, repo: MyApp.Repo

  schema("users", infer: true)

  view(:active) do
    schema([:id, :name, :email])  # Only include specific fields

    derive do
      restrict(active: true)      # Automatically filter active users
    end
  end
end

# Use the view
active_users = MyApp.Users.active().all()  # Returns only active users with limited fields

Examples

Basic View with Field Selection

iex> defmodule BlogApp.Users do
...>   use Drops.Relation, repo: MyApp.Repo
...>   schema("users", infer: true)
...>
...>   view(:active) do
...>     schema([:id, :name, :active])
...>
...>     derive do
...>       restrict(active: true)
...>     end
...>   end
...> end
iex>
iex> # View returns only active users with limited fields
iex> active_users = BlogApp.Users.active().all()
iex> length(active_users)
2
iex> hd(active_users).name
"John Doe"
...>
iex> hd(active_users).active
true
...>
iex> Map.has_key?(hd(active_users), :email)
false

View with Custom Struct Name

iex> defmodule BlogApp.Posts do
...>   use Drops.Relation, repo: MyApp.Repo
...>
...>   schema("posts", infer: true)
...>
...>   view(:published) do
...>     schema([:id, :title, :view_count, :published], struct: "PublishedPost")
...>
...>     derive do
...>       restrict(published: true)
...>       |> order(desc: :view_count)
...>     end
...>   end
...> end
iex>
iex> # View returns published posts ordered by view count
iex> published_posts = BlogApp.Posts.published().all()
iex> length(published_posts)
3
iex> hd(published_posts).__struct__
BlogApp.Posts.Published.PublishedPost
iex> hd(published_posts).title
"First Post"
iex> hd(published_posts).view_count
100

Multiple Views on Same Relation

iex> defmodule BlogApp.Analytics do
...>   use Drops.Relation, repo: MyApp.Repo
...>
...>   schema("posts", infer: true)
...>
...>   view(:popular) do
...>     schema([:id, :title, :view_count, :published])
...>
...>     derive do
...>       restrict(published: true)
...>       |> order(desc: :view_count)
...>     end
...>   end
...>
...>   view(:recent_drafts) do
...>     schema([:id, :title, :user_id, :published])
...>
...>     derive do
...>       restrict(published: false)
...>     end
...>   end
...> end
iex>
iex> # Popular posts view
iex> popular = BlogApp.Analytics.popular().all()
iex> length(popular)
3
iex> hd(popular).title
"First Post"
iex> hd(popular).view_count
100
iex> drafts = BlogApp.Analytics.recent_drafts().all()
iex> length(drafts)
1
iex> hd(drafts).title
"Draft Post"