A repository dedicated to a ruby gem that shows the whole hierarchy and the associations related to a desired class.

Why it is necessary?

Currently, Rails doesn't have an easy way to discover the relations among a bunch of ActiveRecord classes.

For example, if...

1. Person has_many books
2. Book has_many pages
3. Page has_many words
4. Word has_many letters

We need to search inside each one of these files to discover the relations among them. Therefore, we don't have a way to display an overview of all of these relations singlehandedly to help you understand the whole ecosystem of relationships of the model classes.

With the hierarchy-tree gem, it is possible to see this hierarchy ecosystem overview of the classes with ease! 😄

Instalation

Add hierarchy-tree to your Gemfile.

gem 'hierarchy-tree'

Usage

1. Just require the hierarchy_tree library and use it! (You can test this on rails console)

require 'hierarchy_tree'

# Array of hashes of relations → Representing the hierarchy symbolized relations
Hierarchy.associations(YourClass)

# Array of hashes of classes → Representing the hierarchy of relations as stringified classes instead of symbolized relations
Hierarchy.classes(YourClass)

# Array of classes → Just a list of descendant classes, without representing the relations
Hierarchy.classes_list(YourClass)

# Output the classes from leaves to root by using topological sorting
Hierarchy.bottom_up_classes(YourClass)

# Array of relations → Representing all the possible paths starting from the ChildClass until it reaches AncestorClass
Hierarchy.ancestors(from: ChildClass, to: AncestorClass)

# Hash of relations → Representing the ancestors hierarchy starting from the ChildClass until it reaches AncestorClass searching by Depth First Search
Hierarchy.ancestors_dfs(from: ChildClass, to: AncestorClass)

# Hash of relations → Representing the ancestors hierarchy starting from the ChildClass until it reaches AncestorClass searching by Breadth First Search
Hierarchy.ancestors_bfs(from: ChildClass, to: AncestorClass)

# Same as above, but returning an array of classes
Hierarchy.ancestors_bfs(from: ChildClass, to: AncestorClass, classify: true)

Example

• Imagine you have the following classes with their relations...

class Book < ActiveRecord::Base
  has_many :pages
  has_many :words
end

class Page < ActiveRecord::Base
  belongs_to :book
  has_many :lines
  has_many :words
end

class Line < ActiveRecord::Base
  belongs_to :page
  has_many :words
end

class Word < ActiveRecord::Base
  belongs_to :line
  belongs_to :page
  belongs_to :book
  has_many :letters
end

class Letter < ActiveRecord::Base
  belongs_to :word
end

• Then, you can run the following commands (Please, don't forget to require 'hierarchy_tree')

Hierarchy.associations(Book)
# [{:pages=>[{:lines=>[{:words=>[:letters]}]}, {:words=>[:letters]}]}, {:words=>[:letters]}]

Hierarchy.classes(Book)
# [{:pages=>[{:lines=>[{:words=>[:letters]}]}, {:words=>[:letters]}]}, {:words=>[:letters]}]

Hierarchy.classes_list(Book)
# ["Page", "Line", "Word", "Letter"]

Hierarchy.bottom_up_classes(Book)
# ["Letter", "Word", "Line", "Page", "Book"]

Hierarchy.ancestors(from: Letter, to: Book)
# [{:word=>:book}, {:word=>{:page=>:book}}, {:word=>{:line=>{:page=>:book}}}]

Hierarchy.ancestors_dfs(from: Letter, to: Book)
# {:word=>{:line=>{:page=>:book}}}

Hierarchy.ancestors_bfs(from: Letter, to: Book)
# {:word=>:book}

• A nice way to display the associations is through the YAML format without aliases

puts YAML.load(Hierarchy.associations(Book).to_json).to_yaml

The result is...

--- # Book
- pages:
  - lines:
    - words:
      - letters
    - letters
  - words:
    - letters
  - letters
- lines:
  - words:
    - letters
  - letters
- words:
  - letters
- letters

Polymorphic Relations 👨‍👩‍👧‍👦

In case there are polymorphic relations in your database and you want to discover the ancestors path(s) between these classes including the polymorphic relations, you need to explicitly setup the belongs_to association to each class the polymorphic relation is associated.

So, if you have a polymorphic relation like this one for example:

class Request
end

class Scope
end

class Progress
end

class Inspection < ActiveRecord::Base
  belongs_to :inspected, polymorphic: true, optional: true
  # inspected_type = "Request" or "Scope" or "Progress"
end

You need to explicitly add the belongs_to associations related with these models, following the instructions of this answer.

class Inspection < ActiveRecord::Base
  belongs_to :request, -> { where(inspections: { inspected_type: 'Request' }) },
             foreign_key: 'inspected_id', optional: true, inverse_of: :inspections
  belongs_to :scope, -> { where(inspections: { inspected_type: 'Scope' }) },
             foreign_key: 'inspected_id', optional: true, inverse_of: :inspections
  belongs_to :progress, -> { where(inspections: { inspected_type: 'Progress' }) },
             foreign_key: 'inspected_id', optional: true, inverse_of: :inspections
end

By this manner, the hierarchy-tree gem will consider the polymorphic relations inside the paths discovery. 🚀

Contact

• Victor Cordeiro Costa

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*This repository is maintained and developed by Victor Cordeiro Costa. For inquiries, partnerships, or support, don't hesitate to get in touch.