Module: OrderAsSpecified

Defined in:
lib/order_as_specified.rb,
lib/order_as_specified/error.rb,
lib/order_as_specified/version.rb

Overview

This module adds the ability to query an ActiveRecord class for results from the database in an arbitrary order, without having to store anything extra in the database. Simply extend it into your class and then you can use the order_as_specified class method.

Defined Under Namespace

Classes: Error

Constant Summary collapse

VERSION = 
"1.7"

Instance Method Summary collapse

Instance Method Details

#order_as_specified(hash) ⇒ ActiveRecord::Relation 



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# File 'lib/order_as_specified.rb', line 13

def order_as_specified(hash)
  distinct_on = hash.delete(:distinct_on)
  case_insensitive = hash.delete(:case_insensitive)

  params = extract_params(hash)
  return all if params[:values].empty?

  table = Arel::Table.new(params[:table])
  node = Arel::Nodes::Case.new

  params[:values].each_with_index do |value, index|
    attribute = table[params[:attribute]]
    condition =
      if value.is_a?(Range)
        if value.first >= value.last
          raise OrderAsSpecified::Error, "Range needs to be increasing"
        end

        attribute.between(value)
      elsif case_insensitive
        attribute.matches(value)
      else
        attribute.eq(value)
      end

    node.when(condition).then(index)
  end

  node.else(node.conditions.size)
  scope = order(Arel::Nodes::Ascending.new(table.grouping(node)))

  if distinct_on
    distinct = Arel::Nodes::DistinctOn.new(node)
    table_alias = connection.quote_table_name(table.name)
    scope = scope.select(Arel.sql("#{distinct.to_sql} #{table_alias}.*"))
  end

  scope
end