From d5a4d5abb41c50f96b554374b937ffe49d472d7f Mon Sep 17 00:00:00 2001
From: David Heinemeier Hansson <david@loudthinking.com>
Date: Wed, 12 Mar 2008 21:26:02 +0000
Subject: Added ActiveRecord::Base.find(:last) (closes #11338) [miloops]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@9012 5ecf4fe2-1ee6-0310-87b1-e25e094e27de
---
 activerecord/lib/active_record/base.rb | 39 +++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

(limited to 'activerecord/lib/active_record')

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index d5da9408f3..a30036f561 100755
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -430,12 +430,14 @@ module ActiveRecord #:nodoc:
     @@schema_format = :ruby
 
     class << self # Class methods
-      # Find operates with three different retrieval approaches:
+      # Find operates with four different retrieval approaches:
       #
       # * Find by id: This can either be a specific id (1), a list of ids (1, 5, 6), or an array of ids ([5, 6, 10]).
       #   If no record can be found for all of the listed ids, then RecordNotFound will be raised.
       # * Find first: This will return the first record matched by the options used. These options can either be specific
       #   conditions or merely an order. If no record can be matched, nil is returned.
+      # * Find last: This will return the last record matched by the options used. These options can either be specific
+      #   conditions or merely an order. If no record can be matched, nil is returned.
       # * Find all: This will return all the records matched by the options used. If no records are found, an empty array is returned.
       #
       # All approaches accept an options hash as their last parameter. The options are:
@@ -475,6 +477,11 @@ module ActiveRecord #:nodoc:
       #   Person.find(:first, :conditions => [ "user_name = ?", user_name])
       #   Person.find(:first, :order => "created_on DESC", :offset => 5)
       #
+      # Examples for find last:
+      #   Person.find(:last) # returns the last object fetched by SELECT * FROM people
+      #   Person.find(:last, :conditions => [ "user_name = ?", user_name])
+      #   Person.find(:last, :order => "created_on DESC", :offset => 5)
+      #
       # Examples for find all:
       #   Person.find(:all) # returns an array of objects for all the rows fetched by SELECT * FROM people
       #   Person.find(:all, :conditions => [ "category IN (?)", categories], :limit => 50)
@@ -499,6 +506,7 @@ module ActiveRecord #:nodoc:
 
         case args.first
           when :first then find_initial(options)
+          when :last  then find_last(options)
           when :all   then find_every(options)
           else             find_from_ids(args, options)
         end
@@ -1236,6 +1244,35 @@ module ActiveRecord #:nodoc:
           find_every(options).first
         end
 
+        def find_last(options)
+          order = options[:order]
+
+          if order
+            order = reverse_sql_order(order)
+          elsif !scoped?(:find, :order)
+            order = "#{table_name}.#{primary_key} DESC"
+          end
+
+          if scoped?(:find, :order)
+            scoped_order = reverse_sql_order(scope(:find, :order))
+            scoped_methods.select { |s| s[:find].update(:order => scoped_order) }
+          end
+          
+          find_initial(options.merge({ :order => order }))
+        end
+
+        def reverse_sql_order(order_query)
+          reversed_query = order_query.split(/,/).each { |s|
+            if s.match(/\s(asc|ASC)$/)
+              s.gsub!(/\s(asc|ASC)$/, ' DESC')
+            elsif s.match(/\s(desc|DESC)$/)
+              s.gsub!(/\s(desc|DESC)$/, ' ASC')
+            elsif !s.match(/\s(asc|ASC|desc|DESC)$/) 
+              s.concat(' DESC')
+            end
+          }.join(',')
+        end
+        
         def find_every(options)
           include_associations = merge_includes(scope(:find, :include), options[:include])
 
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