module OrderAsSpecified

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.

Constants

VERSION

Public Instance Methods

order_as_specified(hash) click to toggle source

@param hash [Hash] the ActiveRecord arguments hash @return [ActiveRecord::Relation] the objects, ordered as specified

# 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

Private Instance Methods

extract_params(hash, table = table_name) click to toggle source

Recursively search through the hash to find the last elements, which indicate the name of the table we want to condition on, the attribute name, and the attribute values for ordering by. @param table [String/Symbol] the name of the table, default: the class table @param hash [Hash] the ActiveRecord-style arguments, such as:

{ other_objects: { id: [1, 5, 3] } }

# File lib/order_as_specified.rb, line 61
def extract_params(hash, table = table_name)
  unless hash.size == 1
    raise OrderAsSpecified::Error, "Could not parse params"
  end

  key, val = hash.first

  if val.is_a? Hash
    extract_params(hash[key], key)
  else
    {
      table: table,
      attribute: key,
      values: val
    }
  end
end