Module: Glue::NestedSets

Defined in:
lib/glue/hierarchical.rb

Overview

Implements the Nested Sets pattern for hierarchical SQL queries. – TODO: use active collections. ++

Class Method Summary collapse

Class Method Details

.included_with_parameters(base, options) ⇒ Object 



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# File 'lib/glue/hierarchical.rb', line 14

def self.included_with_parameters base, options
  c = {
    :left => 'lft',
    :right => 'rgt',
    :type => Fixnum,
    :parent => base.to_s.demodulize.underscore.downcase,
    :children => base.to_s.demodulize.underscore.downcase.plural
  }
  c.update(options) if options

  parent = "#{c[:parent]}_oid"
  left = c[:left]
  right = c[:right]
  children = c[:children]
  child = children.singular

   if c[:scope].is_a?(Symbol) && c[:scope].to_s !~ /_oid$/
    c[:scope] = "#{c[:scope]}_oid".intern
  end

  scope = c[:scope]

  if scope
    if scope.is_a?(Symbol)
      scope = %{(#{scope} ? "#{scope} = \#{@#{scope}}" : "#{scope} IS NULL")}
    end

    cond = 'condition => ' + scope
    cond_and = ':condition => ' + scope + ' + " AND " +'
  else
    cond = ':condition => nil'
    cond_and = ':condition => '
  end

  base.module_eval <<-EOE, __FILE__, __LINE__    
    property :#{parent}, Fixnum, :sql_index => true
    property :#{left}, :#{right}, #{c[:type]}

    def root?
      (@#{parent}.nil? || @#{parent} == 0) && (@#{left} == 1) && (@#{right} > @#{left})
    end

    def child?
      (@#{parent} &&  @#{parent} != 0) && (@#{left} > 1) && (@#{right} > @#{left})
    end

    def parent
      if root?
        nil
      else
        #{base}[@#{parent}]
      end
    end

    def #{children}_count
      return (@#{right} - @#{left} - 1)/2
    end

    def full_#{children}(options = {})
      options.update(#{cond_and}"(#{left} BETWEEN \#\{@#{left}\} AND \#{@#{right}})")
      #{base}.all(options)
    end

    def #{children}(options = {})
      options.update(#{cond_and}"(#{left} > \#\{@#{left}\}) AND (#{right} < \#{@#{right}})")
      #{base}.all(options)
    end

    def direct_#{children}(options = {})
      options.update(#{cond_and}"#{parent} = \#{pk}")
      #{base}.all(options)
    end

    def add_#{child}(child)
      self.reload if pk
      child.reload if child.pk

      if @#{left}.nil? || @#{left} == 0 || @#{right}.nil? || @#{right} == 0
        @#{left} = 1
        @#{right} = 2 
      end

      child.#{parent} = pk
      child.#{left} = pivot = @#{right}
      child.#{right} = pivot + 1
      @#{right} = pivot + 2

      #{base}.transaction do
        #{base}.update("#{left} = (#{left} + 2)",  #{cond_and}"#{left} >= \#{pivot}")
        #{base}.update("#{right} = (#{right} + 2)", #{cond_and}"#{right} >= \#{pivot}")
      end

      self.save
      child.save
    end
  EOE
end