Gererations methods (#56)

Adds methods to query the current node's level, nodes of the same generation and a hash of all generations grouped by level.

lib/acts_as_tree.rb

@@ -125,6 +125,13 @@ def self.roots
         end
       EOV
 
+      # Returns a hash of all nodes grouped by their level in the tree structure.
+      #
+      # Class.generations { 0=> [root1, root2], 1=> [root1child1, root1child2, root2child1, root2child2] }
+      def self.generations
+        all.group_by{ |node| node.level }
+      end
+
       if configuration[:counter_cache]
         after_update :update_parents_counter_cache
 
@@ -281,6 +288,27 @@ def self_and_siblings
       parent ? parent.children : self.class.roots
     end
 
+    # Returns all the nodes at the same level in the tree as the current node.
+    #
+    #  root1child1.generation [root1child2, root2child1, root2child2]
+    def generation
+      self_and_generation - [self]
+    end
+
+    # Returns a reference to the current node and all the nodes at the same level as it in the tree.
+    #
+    #  root1child1.generation [root1child1, root1child2, root2child1, root2child2]
+    def self_and_generation
+      self.class.select {|node| node.level == self.level }
+    end
+
+    # Returns the level (depth) of the current node
+    #
+    #  root1child1.level 1
+    def level
+      self.ancestors.size
+    end
+
     # Returns children (without subchildren) and current node itself.
     #
     #   root.self_and_children # => [root, child1]

test/acts_as_tree_test.rb

@@ -496,7 +496,6 @@ def test_counter_cache_being_used
   end
 end
 
-
 class TreeTestWithTouch < ActsAsTreeTestCase
   def setup
     setup_db
@@ -541,3 +540,57 @@ def test_nullify
     assert_nil root4_child.reload.external_parent_id
   end
 end
+
+class GenertaionMethods < ActsAsTreeTestCase
+  def setup
+    setup_db
+
+    @root1              = TreeMixin.create!
+    @root_child1        = TreeMixin.create! parent_id: @root1.id
+    @child1_child       = TreeMixin.create! parent_id: @root_child1.id
+    @child1_child_child = TreeMixin.create! parent_id: @child1_child.id
+    @root_child2        = TreeMixin.create! parent_id: @root1.id
+    @root2              = TreeMixin.create!
+    @root2_child1       = TreeMixin.create! parent_id: @root2.id
+    @root2_child2       = TreeMixin.create! parent_id: @root2.id
+    @root2_child1_child = TreeMixin.create! parent_id: @root2_child1.id
+    @root3              = TreeMixin.create!
+  end
+
+  def test_generations
+    assert_equal(
+      {
+        0 => [@root1, @root2, @root3],
+        1 => [@root_child1, @root_child2, @root2_child1, @root2_child2],
+        2 => [@child1_child, @root2_child1_child],
+        3 => [@child1_child_child]
+      },
+      TreeMixin.generations
+    )
+  end
+
+  def test_generation
+    assert_equal [@root2, @root3], @root1.generation
+    assert_equal [@root_child2, @root2_child1, @root2_child2],
+      @root_child1.generation
+    assert_equal [@root2_child1_child], @child1_child.generation
+    assert_equal [], @child1_child_child.generation
+  end
+
+  def test_self_and_generation
+    assert_equal [@root1, @root2, @root3], @root1.self_and_generation
+    assert_equal [@root_child1, @root_child2, @root2_child1, @root2_child2],
+      @root_child1.self_and_generation
+    assert_equal [@child1_child, @root2_child1_child],
+      @child1_child.self_and_generation
+    assert_equal [@child1_child_child], @child1_child_child.self_and_generation
+  end
+
+  def test_level
+    assert_equal 0, @root1.level
+    assert_equal 1, @root_child1.level
+    assert_equal 2, @child1_child.level
+    assert_equal 3, @child1_child_child.level
+  end
+end
+