First version of acts_as_graph_vertex!

.gitignore

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+.DS_Store
+*.gem
+coverage

.rubocop.yml

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+require: rubocop-rspec
+
+LineLength:
+  Max: 120

.travis.yml

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+language: ruby
+rvm:
+  - 2.2.0
+script: bundle exec rspec && bundle exec rubocop

Gemfile

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+source 'https://rubygems.org'
+
+gemspec

Gemfile.lock

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+PATH
+  remote: .
+  specs:
+    acts_as_graph_vertex (1.0.0)
+
+GEM
+  remote: https://rubygems.org/
+  specs:
+    ast (2.0.0)
+    astrolabe (1.3.0)
+      parser (>= 2.2.0.pre.3, < 3.0)
+    byebug (3.5.1)
+      columnize (~> 0.8)
+      debugger-linecache (~> 1.2)
+      slop (~> 3.6)
+    coderay (1.1.0)
+    columnize (0.9.0)
+    coveralls (0.7.8)
+      multi_json (~> 1.10)
+      rest-client (~> 1.7)
+      simplecov (~> 0.9.1)
+      term-ansicolor (~> 1.3)
+      thor (~> 0.19.1)
+    debugger-linecache (1.2.0)
+    diff-lcs (1.2.5)
+    docile (1.1.5)
+    filewatcher (0.3.6)
+      trollop (~> 2.0)
+    method_source (0.8.2)
+    mime-types (2.4.3)
+    multi_json (1.10.1)
+    netrc (0.10.2)
+    parser (2.2.0.2)
+      ast (>= 1.1, < 3.0)
+    powerpack (0.0.9)
+    pry (0.10.1)
+      coderay (~> 1.1.0)
+      method_source (~> 0.8.1)
+      slop (~> 3.4)
+    pry-byebug (2.0.0)
+      byebug (~> 3.4)
+      pry (~> 0.10)
+    rainbow (2.0.0)
+    rest-client (1.7.2)
+      mime-types (>= 1.16, < 3.0)
+      netrc (~> 0.7)
+    rspec (3.1.0)
+      rspec-core (~> 3.1.0)
+      rspec-expectations (~> 3.1.0)
+      rspec-mocks (~> 3.1.0)
+    rspec-core (3.1.7)
+      rspec-support (~> 3.1.0)
+    rspec-expectations (3.1.2)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.1.0)
+    rspec-mocks (3.1.3)
+      rspec-support (~> 3.1.0)
+    rspec-support (3.1.2)
+    rubocop (0.28.0)
+      astrolabe (~> 1.3)
+      parser (>= 2.2.0.pre.7, < 3.0)
+      powerpack (~> 0.0.6)
+      rainbow (>= 1.99.1, < 3.0)
+      ruby-progressbar (~> 1.4)
+    rubocop-rspec (1.2.1)
+    ruby-progressbar (1.7.1)
+    simplecov (0.9.1)
+      docile (~> 1.1.0)
+      multi_json (~> 1.0)
+      simplecov-html (~> 0.8.0)
+    simplecov-html (0.8.0)
+    slop (3.6.0)
+    term-ansicolor (1.3.0)
+      tins (~> 1.0)
+    thor (0.19.1)
+    tins (1.3.3)
+    trollop (2.1.1)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  acts_as_graph_vertex!
+  coveralls (~> 0.7)
+  filewatcher (~> 0.3)
+  pry-byebug (~> 2.0)
+  rspec (~> 3.1)
+  rubocop (~> 0.28)
+  rubocop-rspec (~> 1.2)

README.md

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+# acts_as_graph_vertex [![Build Status](https://travis-ci.org/nathankleyn/acts_as_graph_vertex.svg?branch=master)](https://travis-ci.org/nathankleyn/acts_as_graph_vertex) [![Coverage Status](https://coveralls.io/repos/nathankleyn/acts_as_graph_vertex/badge.png?branch=master)](https://coveralls.io/r/nathankleyn/acts_as_graph_vertex?branch=master)
+
+Simple mixin for adding graph like functions (parents, children, traversal, etc) to any class.
+
+## Installing
+
+You can install this gem via RubyGems:
+
+```sh
+gem install acts_as_graph_vertex
+```
+
+## Using
+
+Sometimes it's useful to be able to add graph like functionality to existing classes you have. This is where acts_as_graph_vertex comes in! Simply mixin this module, and you'll get basic directed acyclic graph (DAG) functionality for free:
+
+```ruby
+require 'acts_as_graph_vertex'
+
+class MyAmazingClass
+  include ActsAsGraphVertex
+end
+```
+
+And now you can use the functions:
+
+```ruby
+parent = MyAmazingClass.new
+child1 = MyAmazingClass.new
+child2 = MyAmazingClass.new
+child3 = MyAmazingClass.new
+
+# The following calls will create a DAG like the following:
+#
+#            --> child1 --
+#          /               \
+# parent--                   --> child3
+#          \               /
+#            --> child2 --
+
+parent.add_child(child1)
+child2.add_parent(child1)
+child3.add_parent(child1)
+child3.add_parent(child2)
+```
+
+You can now traverse the graph from any of these vertices:
+
+```ruby
+parent.children # => [child1, child2]
+parent.all_children # => [child1, child2, child3]
+child3.parents # => [child1, child2]
+child3.all_parents # => [child1, child2, parent]
+```
+
+Note that this mixin does not currently prevent or handle cyclic dependencies; it's intended to be simple rather than exhaustive. If cycle detection is required, using something as a layer over this mixin such as Tarjan's algorithm for finding strongly connected components of a graph is recommended. Tarjan's algorithm is bundled with the Ruby standard library as `TSort` (despite the naming, this class does not provide topographic sorting).
+
+## License
+
+The MIT License (MIT)
+
+Copyright (c) 2015 Nathan Kleyn
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

acts_as_graph_vertex.gemspec

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+$LOAD_PATH.unshift(File.join(__dir__, 'lib'))
+
+Gem::Specification.new do |gem|
+  gem.name = 'acts_as_graph_vertex'
+  gem.version = '1.0.0'
+  gem.homepage = 'https://github.com/nathankleyn/acts_as_graph_vertex'
+  gem.license = 'MIT'
+
+  gem.authors = [
+    'Nathan Kleyn'
+  ]
+  gem.email = [
+    'nathan@nathankleyn.com'
+  ]
+  gem.summary = 'Simple mixin for adding graph like functions (parents, children, traversal, etc) to any class.'
+  gem.description = "See #{gem.homepage} for more information!"
+
+  gem.files = Dir['**/*'].select { |d| d =~ /^(README.md|lib\/)/ }
+
+  gem.add_development_dependency 'coveralls', '~> 0.7'
+  gem.add_development_dependency 'filewatcher', '~> 0.3'
+  gem.add_development_dependency 'pry-byebug', '~> 2.0'
+  gem.add_development_dependency 'rspec', '~> 3.1'
+  gem.add_development_dependency 'rubocop', '~> 0.28'
+  gem.add_development_dependency 'rubocop-rspec', '~> 1.2'
+end

lib/acts_as_graph_vertex.rb

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+# A mixin module enabling classes to have parents and children. It provides
+# convenience methods for determining dependencies, and depdenants.
+#
+# Note that in contrast to a tree, this graph module allows multiple parents.
+module ActsAsGraphVertex
+  # The self.included idiom. This is described in great detail in a
+  # fantastic blog post here:
+  #
+  # http://www.railstips.org/blog/archives/2009/05/15/include-vs-extend-in-ruby/
+  #
+  # Basically, this idiom allows us to add both instance *and* class methods
+  # to the class that is mixing this module into itself without forcing them
+  # to call extend and include for this mixin. You'll see this idiom everywhere
+  # in the Ruby/Rails world, so we use it too.
+  def self.included(cls)
+    cls.extend(ClassMethods)
+  end
+
+  # Common methods inherited by all classes
+  module ClassMethods
+    attr_writer :parents, :children
+  end
+
+  # Public: The parents linked to this instance.
+  #
+  # Returns an Array of Objects.
+  def parents
+    @parents ||= []
+  end
+
+  # Public: The children linked to this instance.
+  #
+  # Returns an Array of Objects.
+  def children
+    @children ||= []
+  end
+
+  # Public: Add a vertex to the parents linked to this instance. Will automatically add as a child of the given parent
+  # if the given parent also mixes in the graph functionality.
+  #
+  # vertex - The Object to add as a parent.
+  # add_child - Whether to add this item as a child of the given parent.
+  def add_parent(vertex, add_child = true)
+    return if parents.include?(vertex)
+    vertex.add_child(self, false) if add_child && vertex.respond_to?(:add_child)
+    parents << vertex
+  end
+
+  # Public: Add a vertex to the children linked to this instance. Will automatically add as a parent of the given child
+  # if the given child also mixes in the graph functionality.
+  #
+  # vertex - The Object to add as a child.
+  # add_parent - Whether to add this item as a parent of the given child.
+  def add_child(vertex, add_parent = true)
+    return if children.include?(vertex)
+    vertex.add_parent(self, false) if add_parent && vertex.respond_to?(:add_parent)
+    children << vertex
+  end
+
+  # Public: Convenience method to return all of the parents from this vertex in
+  # the tree upwards to the root of the tree.
+  #
+  # Returns an Array of parent Objects.
+  def all_parents
+    ((parents + parents.map(&:all_parents)).flatten).uniq
+  end
+
+  # Public: Convenience method to return all of the children from this vertex in
+  # the tree downwards to the leaves of the tree.
+  #
+  # Returns an Array of child Objects.
+  def all_children
+    (children + children.map(&:all_children).flatten).uniq
+  end
+end