Insertion in binary search tree without recursion in ruby

Ruby program for Insertion in binary search tree without recursion. Here more information.

#  Ruby program for
#  iterative insert in binary search tree
class TreeNode 
	# Define the accessor and reader of class TreeNode
	attr_reader :data, :left, :right
	attr_accessor :data, :left, :right
	def initialize(data) 
		self.data = data
		self.left = nil
		self.right = nil
	end
end

class BinarySearchTree 
	# Define the accessor and reader of class BinarySearchTree
	attr_reader :root
	attr_accessor :root
	def initialize() 
		self.root = nil
	end

	# insert a element
	def addNode(data) 
		#  Create a new node
		node = TreeNode.new(data)
		if (self.root == nil) 
			#  When adds a first node in bst
			self.root = node
		else
 
			find = self.root
			#  Add new node to proper position
			while (find != nil) 
				if (find.data >= data) 
					if (find.left == nil) 
						#  When left child empty
						#  So add new node here
						find.left = node
						return
					else
 
						#  Otherwise
						#  Visit left sub-tree
						find = find.left
					end

				else
 
					if (find.right == nil) 
						#  When right child empty
						#  So add new node here
						find.right = node
						return
					else
 
						#  Visit right sub-tree
						find = find.right
					end
				end
			end
		end
	end

	#  Display preorder
	def preorder(node) 
		if (node != nil) 
			#  Display node value
			print("  ", node.data)
			#  Visit to left subtree
			self.preorder(node.left)
			#  Visit to right subtree
			self.preorder(node.right)
		end

	end

	def inorder(node) 
		if (node != nil) 
			#  Visit to left subtree
			self.inorder(node.left)
			#  Display node value
			print("  ", node.data)
			#  Visit to right subtree
			self.inorder(node.right)
		end

	end

	def postorder(node) 
		if (node != nil) 
			#  Visit to left subtree
			self.postorder(node.left)
			#  Visit to right subtree
			self.postorder(node.right)
			#  Display node value
			print("  ", node.data)
		end
	end
end

def main() 
	tree = BinarySearchTree.new()
	#         10
	#        / \
	#       /   \
	#      4     15
	#     / \   /
	#    3   5 12
	#    -------------
	#    Build binary search tree
	tree.addNode(10)
	tree.addNode(4)
	tree.addNode(3)
	tree.addNode(5)
	tree.addNode(15)
	tree.addNode(12)
	#  Display tree nodes
	print("Preorder \n")
	tree.preorder(tree.root)
	print("\nInorder \n")
	tree.inorder(tree.root)
	print("\nPostorder \n")
	tree.postorder(tree.root)
end

main()

Output

Preorder 
  10  4  3  5  15  12
Inorder 
  3  4  5  10  12  15
Postorder 
  3  5  4  12  15  10