dmarkow · renatorfr · Mar 11, 2021 · Mar 15, 2021 · Mar 16, 2021 · Mar 16, 2021
diff --git a/README.md b/README.md
@@ -20,7 +20,7 @@ To get started:
 - ```import EctoRanked```
 - Add a `:rank` integer field to your model (NOTE: Setting a unique index on this column may cause issues depending on your database platform)
 - Call `set_rank()` in your changeset
-- Optionally, add a virtual `:position` field (with a type of `:any`) so you can move items in your list.
+- Optionally, add a virtual `:position` field (with a type of `:any`) so you can move items in your list. `:position` accepts `:up`, `:down`, `:first`, `:last` or an integer, the integer being the desired position in a 0-based index.
 
 ```elixir
 defmodule MyApp.Item do
@@ -99,6 +99,20 @@ struct
 |> set_rank(rank: :global_rank, position: :global_position)
 ```
 
+You can also pass a `:base_queryable` to scope more complex cases:
+
+```elixir
+def changeset(struct, params) do
+  struct
+  |> cast(params, [:position])
+  |> set_rank(base_queryable: &not_deleted_query/2)
+end
+
+def not_deleted_query(module, _options) do
+  from(items in module, where: not is_nil(items.deleted))
+end
+```
+
 Position is a write-only virtual attribute that's meant for placing an item at
 a specific rank. By default the `position` attribute  will be `nil` but you can
 calculate it on demand:

diff --git a/lib/ecto_ranked.ex b/lib/ecto_ranked.ex
@@ -27,7 +27,8 @@ defmodule EctoRanked do
           scope_field: Keyword.get(opts, :scope),
           position_field: Keyword.get(opts, :position, :position),
           rank_field: Keyword.get(opts, :rank, :rank),
-          prefix: Keyword.get(opts, :prefix, nil)
+          prefix: Keyword.get(opts, :prefix, nil),
+          base_queryable: Keyword.get(opts, :base_queryable)
         }
 
         cs
@@ -294,7 +295,8 @@ defmodule EctoRanked do
 
   defp finder(cs, options) do
     query =
-      options.module
+      options
+      |> base_query()
       |> scope_query(cs, options.scope_field)
 
     if cs.data.id do
@@ -304,6 +306,12 @@ defmodule EctoRanked do
     end
   end
 
+  defp base_query(%{base_queryable: base_queryable, module: module} = options)
+       when not is_nil(base_queryable),
+       do: apply(base_queryable, [module, options])
+
+  defp base_query(options), do: options.module
+
   defp scope_query(query, cs, scope_field) when is_list(scope_field) do
     Enum.reduce(scope_field, query, fn field, acc ->
       scope_query(acc, cs, field)

diff --git a/priv/repo/migrations/20210315102137_base_queryable.exs b/priv/repo/migrations/20210315102137_base_queryable.exs
@@ -0,0 +1,10 @@
+defmodule EctoRanked.Test.Repo.Migrations.PrefixedModel do
+  use Ecto.Migration
+
+  def change do
+    create table(:base_queryable_models) do
+      add :my_field, :string, null: true
+      add :rank, :integer, null: false
+    end
+  end
+end
diff --git a/test/base_queryable_test.exs b/test/base_queryable_test.exs
@@ -0,0 +1,34 @@
+defmodule EctoRanked.BaseQueryableTest do
+  use EctoRanked.TestCase
+  import Ecto.Query
+  alias EctoRa
8000
nked.Test.{BaseQueryableModel, Repo}
+
+  def ranked_ids() do
+    BaseQueryableModel
+    |> select([m], m.id)
+    |> order_by(:rank)
+    |> Repo.all()
+  end
+
+  test "moving an item with a base queryable" do
+    model1 =
+      %BaseQueryableModel{}
+      |> BaseQueryableModel.changeset(%{my_field: "My field"})
+      |> Repo.insert!()
+
+    model2 =
+      %BaseQueryableModel{}
+      |> BaseQueryableModel.changeset(%{})
+      |> Repo.insert!()
+
+    model3 =
+      %BaseQueryableModel{}
+      |> BaseQueryableModel.changeset(%{my_field: "My field"})
+      |> Repo.insert!()
+
+    model3 =
+      model3 |> BaseQueryableModel.base_queryable_changeset(%{position: :up}) |> Repo.update!()
+
+    assert ranked_ids() == [model3.id, model1.id, model2.id]
+  end
+end
diff --git a/test/support/base_queryable_model.ex b/test/support/base_queryable_model.ex
@@ -0,0 +1,29 @@
+defmodule EctoRanked.Test.BaseQueryableModel do
+  use Ecto.Schema
+  import Ecto.Changeset
+  import Ecto.Query
+  import EctoRanked
+
+  schema "base_queryable_models" do
+    field :my_field, :string
+    field :rank, :integer
+    field :position, :any, virtual: true
+  end
+
+  def changeset(model, params) do
+    model
+    |> cast(params, [:my_field])
+    |> set_rank()
+  end
+
+  def base_queryable_changeset(model, params) do
+    model
+    |> cast(params, [:position])
+    |> set_rank(base_queryable: &build_base_queryable/2)
+  end
+
+  defp build_base_queryable(module, _options) do
+    module
+    |> where([m], not is_nil(m.my_field))
+  end
+end