Added Base.exists?(id) that'll return true if an object of the class with the given id exists #854 [stian@grytoyr.net]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@913 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Added Base.exists?(id) that'll return true if an object of the class with the given id exists #854 [stian@grytoyr.net]
+
 * Added optionally allow for nil or empty strings with validates_numericality_of #801 [Sebastian Kanthak]
 
 * Fixed problem with using slashes in validates_format_of regular expressions #801 [Sebastian Kanthak]

activerecord/lib/active_record/base.rb

@@ -326,6 +326,13 @@ module ActiveRecord #:nodoc:
         end
       end
 
+      # Returns true if the given +id+ represents the primary key of a record in the database, false otherwise.
+      # Example:
+      #   Person.exists?(5)
+      def exists?(id)
+        !find_first("#{primary_key} = #{sanitize(id)}").nil?
+      end
+
       # This method is deprecated in favor of find with the :conditions option.
       # Works like find, but the record matching +id+ must also meet the +conditions+.
       # +RecordNotFound+ is raised if no record can be found matching the +id+ or meeting the condition.

activerecord/test/finder_test.rb

@@ -10,6 +10,13 @@ class FinderTest < Test::Unit::TestCase
     assert_equal(@topics["first"]["title"], Topic.find(1).title)
   end
   
+  def test_exists
+    assert (Topic.exists?(1))
+    assert !(Topic.exists?(45))
+    assert !(Topic.exists?("foo"))
+    assert !(Topic.exists?([1,2]))
+  end
+  
   def test_find_by_array_of_one_id
     assert_kind_of(Array, Topic.find([ 1 ]))
        assert_equal(1, Topic.find([ 1 ]).length)