Module: ClosureTree::HasClosureTreeRoot

Defined in:
lib/closure_tree/has_closure_tree_root.rb

Instance Method Summary collapse

Instance Method Details

#has_closure_tree_root(assoc_name, options = {}) ⇒ Object 



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# File 'lib/closure_tree/has_closure_tree_root.rb', line 6

def has_closure_tree_root(assoc_name, options = {})
  options.assert_valid_keys(
    :class_name,
    :foreign_key
  )

  options[:class_name] ||= assoc_name.to_s.sub(/\Aroot_/, "").classify
  options[:foreign_key] ||= self.name.underscore << "_id"

  has_one assoc_name, -> { where(parent: nil) }, options

  # Fetches the association, eager loading all children and given associations
  define_method("#{assoc_name}_including_tree") do |assoc_map_or_reload = nil, assoc_map = nil|
    reload = false
    if assoc_map_or_reload.is_a?(::Hash)
      assoc_map = assoc_map_or_reload
    else
      reload = assoc_map_or_reload
    end

    unless reload
      # Memoize
      @closure_tree_roots ||= {}
      @closure_tree_roots[assoc_name] ||= {}
      if @closure_tree_roots[assoc_name].has_key?(assoc_map)
        return @closure_tree_roots[assoc_name][assoc_map]
      end
    end

    roots = options[:class_name].constantize.where(parent: nil, options[:foreign_key] => id).to_a

    return nil if roots.empty?

    if roots.size > 1
      raise MultipleRootError.new("#{self.class.name}: has_closure_tree_root requires a single root")
    end

    temp_root = roots.first
    root = nil
    id_hash = {}
    parent_col_id = temp_root.class._ct.options[:parent_column_name]

    # Lookup inverse belongs_to association reflection on target class.
    inverse = temp_root.class.reflections.values.detect do |r|
      r.macro == :belongs_to && r.klass == self.class
    end

    # Fetch all descendants in constant number of queries.
    # This is the last query-triggering statement in the method.
    temp_root.self_and_descendants.includes(assoc_map).each do |node|
      id_hash[node.id] = node
      parent_node = id_hash[node[parent_col_id]]

      # Pre-assign parent association
      parent_assoc = node.association(:parent)
      parent_assoc.loaded!
      parent_assoc.target = parent_node

      # Pre-assign children association as empty for now,
      # children will be added in subsequent loop iterations
      children_assoc = node.association(:children)
      children_assoc.loaded!

      if parent_node
        parent_node.association(:children).target << node
      else
        # Capture the root we're going to use
        root = node
      end

      # Pre-assign inverse association back to this class, if it exists on target class.
      if inverse
        inverse_assoc = node.association(inverse.name)
        inverse_assoc.loaded!
        inverse_assoc.target = self
      end
    end

    @closure_tree_roots[assoc_name][assoc_map] = root
  end
end