as_nested_set

An ecto based Nested set model implementation for database

Installation

Add as_nested_set to your list of dependencies in mix.exs:

  # use the stable version
  def deps do
    [{:as_nested_set, "~> 3.1", app: false}]
  end

  # use the latest version
  def deps do
    [{:as_nested_set, github: "https://github.com/secretworry/as_nested_set.git", app: false}]
  end

Usage

To make use of as_nested_set your model has to have at least 4 fields: id, lft, rgt and parent_id. The name of those fields are configurable.

defmodule AsNestedSet.TestRepo.Migrations.MigrateAll do
  use Ecto.Migration

  def change do
    create table(:taxons) do
      add :name, :string
      add :taxonomy_id, :id
      add :parent_id, :id
      add :lft, :integer
      add :rgt, :integer

      timestamps
    end

  end
end

Enable the nested set functionality by use AsNestedSet on your model

defmodule AsNestedSet.Taxon do
  use AsNestedSet, scope: [:taxonomy_id]
  # ...
end

Options

You can config the name of required field through attributes:

defmodule AsNestedSet.Taxon do
  @right_column :right
  @left_column :left
  @node_id_column :node_id
  @parent_id_column :pid
  # ...
end

• @right_column: column name for right boundary (default to lft, since left is a reserved keyword for Mysql)
• @left_column: column name for left boundary (default to rgt, reserved too)
• @node_id_column: specifies the name for the node id column (default to id, i.e. the id of the model, change this if you want to have a different id, or you id field is different)
• @parent_id_column: specifies the name for the parent id column (default to parent_id)

You can also pass following to modify its behavior:

defmodule AsNestedSet.Taxon do
  use AsNestedSet, scope: [:taxonomy_id]
  # ...
end

• scope: (required) a list of column names which restrict what is to be considered within the same tree(same scope).

Model Operations

Once you have set up you model, you can then

Add a new node

target = Repo.find!(Taxon, 1)
# add to left
%Taxon{name: "left", taxonomy_id: 1} |> AsNestedSet.create(target, :left) |> AsNestedSet.execute(TestRepo)
# add to right
%Taxon{name: "right", taxonomy_id: 1} |> AsNestedSet.create(target, :right) |> AsNestedSet.execute(TestRepo)
# add as first child
%Taxon{name: "child", taxonomy_id: 1} |> AsNestedSet.create(target, :child) |> AsNestedSet.execute(TestRepo)
# add as parent
%Taxon{name: "parent", taxonomy_id: 1} |> AsNestedSet.create(target, :parent) |> AsNestedSet.execute(TestRepo)

# add as root
%Taxon{name: "root", taxonomy_id: 1} |> AsNestedSet.create(:root) |> AsNestedSet.execute(TestRepo)

# move a node to a new position

node |> AsNestedSet.move(:root) |> AsNestedSet.execute(TestRepo)
node |> AsNestedSet.move(target, :left) |> AsNestedSet.execute(TestRepo)
node |> AsNestedSet.move(target, :right) |> AsNestedSet.execute(TestRepo)
node |> AsNestedSet.move(target, :child) |> AsNestedSet.execute(TestRepo)

Remove a specified node and all its descendants

target = Repo.find!(Taxon, 1)
AsNestedSet.remove(target) |> AsNestedSet.execute(TestRepo)

Query different nodes

# find all roots
AsNestedSet.roots(Taxon, %{taxonomy_id: 1}) |> AsNestedSet.execute(TestRepo)

# find all children of target
AsNestedSet.children(target) |> AsNestedSet.execute(TestRepo)

# find all the leaves for given scope
AsNestedSet.leaves(Taxon, %{taxonomy_id: 1}) |> AsNestedSet.execute(TestRepo)

# find all descendants
AsNestedSet.descendants(target) |> AsNestedSet.execute(TestRepo)
# include self
AsNestedSet.self_and_descendants(target) |> AsNestedSet.execute(TestRepo)

# find all ancestors
AsNestedSet.ancestors(target) |> AsNestedSet.execute(TestRepo)

#find all siblings (self included)
AsNestedSet.self_and_siblings(target) |> AsNestedSet.execute(TestRepo)

Traverse the tree

# traverse a tree with 3 args post callback
AsNestedSet.traverse(Taxon, %{taxonomy_id}, context, fn node, context -> {node, context}, end, fn node, children, context -> {node, context} end) |> AsNestedSet.execute(TestRepo)
# traverse a tree with 2 args post callback
AsNestedSet.traverse(Taxon, %{taxonomy_id}, context, fn node, context -> {node, context}, end, fn node, context -> {node, context} end) |> AsNestedSet.execute(TestRepo)

# traverse a subtree with 3 args post callback
AsNestedSet.traverse(target, context, fn node, context -> {node, context}, end, fn node, children, context -> {node, context} end) |> AsNestedSet.execute(TestRepo)
# traverse a tree with 2 args post callback
AsNestedSet.traverse(target, context, fn node, context -> {node, context}, end, fn node, context -> {node, context} end) |> AsNestedSet.execute(TestRepo)