added sibling functionality

lib/treeify.rb

@@ -49,7 +49,19 @@ def tree_sql_for(instance)
     end
 
     def tree_sql_for_ancestors(instance)
-      "#{tree_sql(instance)}
+      "WITH RECURSIVE cte (id, path)  AS (
+         SELECT  id,
+           array[id] AS path
+         FROM    #{table_name}
+         WHERE   id = #{instance.id}
+         
+         UNION ALL
+
+         SELECT  #{table_name}.id,
+            cte.path || #{table_name}.id
+         FROM    #{table_name}
+         JOIN cte ON #{table_name}.parent_id = cte.id
+       )
       SELECT cte.id FROM cte WHERE cte.id != #{instance.id}"
     end
   end
@@ -65,4 +77,12 @@ def ancestors
   def self_and_descendents
     self.class.tree_for(self)
   end
+
+  def is_root?
+    self.parent_id != nil
+  end
+
+  def siblings
+    self.class.where(parent_id: self.parent_id) - [self]
+  end
 end 

spec/treeify_spec.rb

@@ -59,17 +59,36 @@
       expect(Node.where(name: "new child node").take).to eq(nil)
     end
 
-    it "adds children to child nodes"
+    it "adds children to child nodes" do
+      root = Node.roots.first
+      child = root.children.create(name: "new child node")
+      subchild = child.children.create(name: "new subchild node")
+      expect(child.children.count).to eq(1)
+    end
 
-    it "has the correct tree after subchildren are added"
+    it "has the correct tree after subchildren are added" do
+      tree = Node.roots.first.self_and_descendents
+      tree.each do |node|
+        pending "Ancestor count for parent nodes doesn't work yet"
+        if node.parent_id.nil?
+          expect(node.ancestors.count).to eq(0)
+        end
+      end
+    end
 
     it "deletes subchildren"
 
     it "re-parents children"
 
     it "has the correct tree after children are re-parented"
 
-    it "retrieves siblings"
+    it "retrieves siblings" do
+      10.times do |n|
+        Node.create(name: "sib_#{n}", parent_id: Node.roots.first.id)
+      end
+      sib = Node.where(name: "sib_1").take
+      expect(sib.siblings.count).to eq(12)
+    end
 
     it "adds siblings"