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 = 
"1.3"

Instance Method Summary collapse

Instance Method Details

#order_as_specified(hash) ⇒ ActiveRecord::Relation

Returns the objects, ordered as specified.

Parameters:

  • hash (Hash) —

    the ActiveRecord arguments hash

Returns:

  • (ActiveRecord::Relation) —

    the objects, ordered as specified



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# File 'lib/order_as_specified.rb', line 12

def order_as_specified(hash)
  distinct_on = hash.delete(:distinct_on)
  params = extract_params(hash)

  table = connection.quote_table_name(params[:table])
  attribute = connection.quote_column_name(params[:attribute])

  # We have to explicitly quote for now because SQL sanitization for ORDER BY
  # queries isn't in less current versions of Rails.
  # See: https://github.com/rails/rails/pull/13008
  db_connection = ActiveRecord::Base.connection
  conditions = params[:values].map do |value|
    raise OrderAsSpecified::Error, "Cannot order by `nil`" if value.nil?

    # Sanitize each value to reduce the risk of SQL injection.
    "#{table}.#{attribute}=#{db_connection.quote(value)}"
  end

  scope = order(conditions.map { |cond| "#{cond} DESC" }.join(", "))

  if distinct_on
    scope = scope.select("DISTINCT ON (#{conditions.join(', ')}) #{table}.*")
  end

  scope
end