ancestors, descendants added. Detached node

models/tree.rb

@@ -24,4 +24,59 @@ def leaf?
   def siblings
     root? ? [] : parent.children - [self]
   end
-end
+
+
+  def to_s
+    @name
+  end
+
+
+  # Similar to acts_as_tree .descendants method
+  # each_with_object will put each child into the do/|| block in the 'child' variable.
+  # array_of_children comes from the first argument from each_with_object, in this case
+  # we are giving 'each_with_object' the 'children' array.
+  # You could change children to @children because it is an instance variable.
+  # array_of_children is modified with each iteration.
+  def descendants
+    # This line is talking about the direct children (Paul, Peter and Mary,
+    # if you were starting with Fred.)
+    children.each_with_object(children) { |child, array_of_children|
+      # This line is talking the grand children and so forth (following on,
+      # Pan and Rabbit).
+      array_of_children.concat child.descendants
+      # uniq ensures that no children get counted twice (shouldn't happen anyway)
+    }.uniq
+  end
+
+
+
+  def ancestors
+    # This commented out part was taken directly from acts_as_tree
+    # changed it to be more understandable.
+    # They both do the same thing.
+    # node, nodes = self, []
+    # nodes << node = node.parent while node.parent
+    # nodes
+
+    current_tree = self
+    trees = []
+    # Assuming grandchild1 is given, this will iterate twice.
+    # current_tree will initially be grandchild1
+    # after the first loop, it will become child1
+    # after the second loop it will become parent.
+    # Then the loop will end, because parent is an orphan.
+    while current_tree && current_tree.parent
+      current_tree = current_tree.parent
+      # << this is the same as trees.push
+      trees << current_tree
+    end
+    # Going on that assumption, the final array would be (child1, parent).
+    trees
+  end
+
+
+  def detach_node!
+    parent.children.delete self
+    @parent = nil
+  end
+end

specs/models/tree_spec.rb

@@ -101,4 +101,65 @@
       expect(fred.leaf?).to be_falsey
     end
   end
+
+  describe '.descendants' do
+    it 'makes an array of all children of children of children, etc' do
+      parent = Tree.new('Parent')
+      child1 = Tree.new('Child1')
+      child2 = Tree.new('Child2')
+      grandchild1 = Tree.new('Grandchild1')
+      grandchild2 = Tree.new('Grandchild2')
+
+      parent.add_child(child1)
+      parent.add_child(child2)
+
+      child1.add_child(grandchild1)
+      child1.add_child(grandchild2)
+
+
+      descendants = parent.descendants
+      expect(descendants).to include(child1, child2, grandchild1, grandchild2)
+      expect(descendants).to_not include(parent)
+    end
+  end
+
+  describe '.ancestors' do
+    it 'makes an array of all ancestors' do
+      parent = Tree.new('Parent')
+      child1 = Tree.new('Child1')
+      child2 = Tree.new('Child2')
+      grandchild1 = Tree.new('Grandchild1')
+      grandchild2 = Tree.new('Grandchild2')
+
+      parent.add_child(child1)
+      parent.add_child(child2)
+
+      child1.add_child(grandchild1)
+      child1.add_child(grandchild2)
+
+      ancestors = grandchild1.ancestors
+      expect(ancestors).to include(child1, parent)
+      expect(ancestors).to_not include(child2, grandchild2)
+    end
+  end
+
+  describe '.detach_node' do
+    it 'removes itself from its parent. The child becomes emancipated.' do
+      parent = Tree.new('Parent')
+      child1 = Tree.new('Child1')
+      child2 = Tree.new('Child2')
+      grandchild1 = Tree.new('Grandchild1')
+      grandchild2 = Tree.new('Grandchild2')
+
+      parent.add_child(child1)
+      parent.add_child(child2)
+
+      child1.add_child(grandchild1)
+      child1.add_child(grandchild2)
+
+      child1.detach_node!
+      expect(parent.children).to_not include(child1)
+      expect(child1.parent).to_not eq(parent)
+    end
+  end
 end