If you have any class which requires access to some path methods generated by your routes. Even though you could technically include Rails.application.routes.url_helpers, this may include way too many methods and even overwrite some class methods in the worst case.

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Instead, most of the time the following is advised to only make the desired methods available:

class Project
  delegate :url_helpers, to: 'Rails.application.routes'

  def project_path
    url_helpers.project_path(self)
  end
end