module Sequel::Plugins::Tree

  1. lib/sequel/plugins/tree.rb

The tree plugin adds additional associations and methods that allow you to treat a Model as a tree.

A column for holding the parent key is required and is :parent_id by default.

This may be overridden by passing column name via :key.

Optionally, a column to control order of nodes returned can be specified by passing column name via :order.

If you pass true for the :single_root option, the class will ensure there is only ever one root in the tree.

Examples:

class Node < Sequel::Model
  plugin :tree
end

class Node < Sequel::Model
  plugin :tree, key: :parentid, order: :position
end

Methods

Public Class

  1. apply

Public Class methods

apply (model, opts=OPTS)

Create parent and children associations. Any options specified are passed to both associations. You can also specify options to use for just the parent association using a :parent option, and options to use for just the children association using a :children option.

[show source]
# File lib/sequel/plugins/tree.rb, line 31
def self.apply(model, opts=OPTS)
  opts = opts.dup
  opts[:class] = model
  opts[:key] ||= :parent_id

  par = opts.merge(opts.fetch(:parent, OPTS))
  parent = par.fetch(:name, :parent)
  
  chi = opts.merge(opts.fetch(:children, OPTS))
  children = chi.fetch(:name, :children)

  par[:reciprocal] = children
  chi[:reciprocal] = parent

  model.instance_exec do
    @parent_column = opts[:key]
    @tree_order = opts[:order]
    @parent_association_name = parent
    @children_association_name = children

    many_to_one parent, par
    one_to_many children, chi
    plugin SingleRoot if opts[:single_root]
  end
end