A long-lived project that still receives updates
RubyTree is a Ruby implementation of the generic tree data structure. It provides simple APIs to store named nodes, and to access, modify, and traverse the tree. The data model is node-centric, where nodes in the tree are the primary structural elements. It supports all common tree-traversal methods (pre-order, post-order, and breadth first). RubyTree mixes in the Enumerable and Comparable modules and behaves like a standard Ruby collection (iteration, comparison, etc.). RubyTree also includes a binary tree implementation, which provides in-order node traversal besides the other methods. RubyTree can import from and export to JSON, and supports Ruby’s object marshaling.


~> 2.3
~> 13.0
~> 6.0
~> 3.0, > 3.10
~> 0.0.4
~> 1.0
~> 3.0
~> 0.0, >= 0.9.20
~> 0.21


~> 2.0, > 2.3.1
 Project Readme


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RubyTree is a pure Ruby implementation of the generic tree data structure. It provides a node-based model to store named nodes in the tree, and provides simple APIs to access, modify and traverse the structure.

The implementation is node-centric, where individual nodes in the tree are the primary structural elements. All common tree-traversal methods (pre-order, post-order, and breadth-first) are supported.

The library mixes in the Enumerable and Comparable modules to allow access to the tree as a standard collection (iteration, comparison, etc.).

A Binary tree is also provided, which provides the in-order traversal in addition to the other methods.

RubyTree supports importing from, and exporting to JSON, and also supports the Ruby's standard object marshaling.

This is a BSD licensed open source project, and is hosted at github.com/evolve75/RubyTree, and is available as a standard gem from rubygems.org/gems/rubytree.

The home page for RubyTree is at rubytree.anupamsg.me.


See History for the detailed Changelog.

See API-CHANGES for the detailed description of API level changes.


This is a basic usage example of the library to create and manipulate a tree. See the API documentation for more details.

#!/usr/bin/env ruby
# example_basic.rb:: Basic usage of the tree library.
# Copyright (C) 2013-2022 Anupam Sengupta <anupamsg@gmail.com>
# The following example implements this tree structure:
#                    +------------+
#                    |    ROOT    |
#                    +-----+------+
#            +-------------+------------+
#            |                          |
#    +-------+-------+          +-------+-------+
#    |  CHILD 1      |          |  CHILD 2      |
#    +-------+-------+          +---------------+
#            |
#            |
#    +-------+-------+
#    | GRANDCHILD 1  |
#    +---------------+

# ..... Example starts.
require 'tree'                 # Load the library

# ..... Create the root node first.
# ..... Note that every node has a name and an optional content payload.
root_node = Tree::TreeNode.new("ROOT", "Root Content")

# ..... Now insert the child nodes.
#       Note that you can "chain" the child insertions to any depth.
root_node << Tree::TreeNode.new("CHILD1", "Child1 Content") << Tree::TreeNode.new("GRANDCHILD1", "GrandChild1 Content")
root_node << Tree::TreeNode.new("CHILD2", "Child2 Content")

# ..... Lets print the representation to stdout.
# ..... This is primarily used for debugging purposes.

# ..... Lets directly access children and grandchildren of the root.
# ..... The can be "chained" for a given path to any depth.
child1       = root_node["CHILD1"]
grand_child1 = root_node["CHILD1"]["GRANDCHILD1"]

# ..... Now retrieve siblings of the current node as an array.
siblings_of_child1 = child1.siblings

# ..... Retrieve immediate children of the root node as an array.
children_of_root = root_node.children

# ..... Retrieve the parent of a node.
parent = child1.parent

# ..... This is a depth-first and L-to-R pre-ordered traversal.
root_node.each { |node| node.content.reverse }

# ..... Remove a child node from the root node.

# .... Many more methods are available. Check out the documentation!

This example can also be found at examples/example_basic.rb.


  • Ruby 2.6.x and above.

  • Run-time Dependencies:

    • JSON for converting to/from the JSON format
  • Development dependencies (not required for installing the gem):

    • Bundler for creating the stable build environment
    • Rake for building the package
    • Yard for the documentation
    • RSpec for additional Ruby Spec test files
    • Rubocop for linting the code


To install the gem, run this command from a terminal/shell:

$ gem install rubytree

This should install the gem file for RubyTree. Note that you might need to have super-user privileges (root/sudo) to successfully install the gem.


The primary class RubyTree is Tree::TreeNode. See the class documentation for an example of using the library.

If the ri documentation was generated during install, you can use this command at the terminal to view the text mode ri documentation:

$ ri Tree::TreeNode

Documentation for the latest released version is available at:


Documentation for the latest git HEAD is available at:


Note that the documentation is formatted using Yard.


This section is only for modifying RubyTree itself. It is not required for using the library!

You can download the latest released source code as a tar or zip file, as mentioned above in the installation section.

Alternatively, you can checkout the latest commit/revision from the Version Control System. Note that RubyTree's primary SCM is git and is hosted on github.com.

Using the git Repository

The git repository is available at github.com/evolve75/RubyTree.

For cloning the git repository, use one of the following commands:

$ git clone git://github.com/evolve75/RubyTree.git    # using ssh


$ git clone https://github.com/evolve75/RubyTree.git  # using https

Setting up the Development Environment

RubyTree uses Bundler to manage its dependencies. This allows for a simplified dependency management, for both run-time as well as during build.

After checking out the source, run:

$ gem install bundler
$ bundle install
$ bundle exec rake test:all
$ bundle exec rake doc:yard
$ bundle exec rake gem:package

These steps will install any missing dependencies, run the tests/specs, generate the documentation, and finally generate the gem file.

Note that the documentation uses Yard, which will be downloaded and installed automatically by Bundler.


A big thanks to the following contributors for helping improve RubyTree:

  1. Dirk Breuer for contributing the JSON conversion code.
  2. Vincenzo Farruggia for contributing the (sub)tree cloning code.
  3. Eric Cline for the Rails JSON encoding fix.
  4. Darren Oakley for the tree merge methods.
  5. Youssef Rebahi-Gilbert for the code to check duplicate node names in the tree (globally unique names).
  6. Paul de Courcel for adding the postordered_each method.
  7. Jen Hamon for adding the from_hash method.
  8. Evan Sharp for adding the rename and rename_child methods.
  9. Aidan Steele for performance improvements to is_root? and node_depth.
  10. Marco Ziccadi for adding the path_as_string and path_as_array methods.
  11. John Mortlock for significant modernization of the library code and addition of Github workflows.
  12. Hermann Mayer for adding support for specialized tree nodes (sub-classes of Tree::TreeNode).
  13. Jakub Pavlik for fixing the creation of detached copies of unclonable objects such as :symbol, true|false, etc.


RubyTree is licensed under the terms of the BSD license. See LICENSE.md for details.