diff options
| -rw-r--r-- | activerecord/lib/active_record/relation/finder_methods.rb | 27 | ||||
| -rw-r--r-- | activerecord/test/cases/finder_test.rb | 60 |
2 files changed, 83 insertions, 4 deletions
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb index 0037398554..c3053f0b13 100644 --- a/activerecord/lib/active_record/relation/finder_methods.rb +++ b/activerecord/lib/active_record/relation/finder_methods.rb @@ -255,13 +255,13 @@ module ActiveRecord # Person.offset(3).third_to_last # returns the third-to-last object from OFFSET 3 # Person.where(["user_name = :u", { u: user_name }]).third_to_last def third_to_last - find_nth(-3) + find_nth_from_last 3 end # Same as #third_to_last but raises ActiveRecord::RecordNotFound if no record # is found. def third_to_last! - find_nth!(-3) + find_nth_from_last 3 or raise RecordNotFound.new("Couldn't find #{@klass.name} with [#{arel.where_sql(@klass.arel_engine)}]") end # Find the second-to-last record. @@ -271,13 +271,13 @@ module ActiveRecord # Person.offset(3).second_to_last # returns the second-to-last object from OFFSET 3 # Person.where(["user_name = :u", { u: user_name }]).second_to_last def second_to_last - find_nth(-2) + find_nth_from_last 2 end # Same as #second_to_last but raises ActiveRecord::RecordNotFound if no record # is found. def second_to_last! - find_nth!(-2) + find_nth_from_last 2 or raise RecordNotFound.new("Couldn't find #{@klass.name} with [#{arel.where_sql(@klass.arel_engine)}]") end # Returns true if a record exists in the table that matches the +id+ or @@ -561,6 +561,25 @@ module ActiveRecord relation.limit(limit).to_a end + def find_nth_from_last(index) + if loaded? + @records[-index] + else + relation = if order_values.empty? && primary_key + order(arel_attribute(primary_key).asc) + else + self + end + + relation.to_a[-index] + # TODO: can be made more performant on large result sets by + # for instance, last(index)[-index] (which would require + # refactoring the last(n) finder method to make test suite pass), + # or by using a combination of reverse_order, limit, and offset, + # e.g., reverse_order.offset(index-1).first + end + end + private def find_nth_with_limit_and_offset(index, limit, offset:) # :nodoc: diff --git a/activerecord/test/cases/finder_test.rb b/activerecord/test/cases/finder_test.rb index 3e31874455..692c6bf2d0 100644 --- a/activerecord/test/cases/finder_test.rb +++ b/activerecord/test/cases/finder_test.rb @@ -486,6 +486,66 @@ class FinderTest < ActiveRecord::TestCase end end + def test_second_to_last + assert_equal topics(:fourth).title, Topic.second_to_last.title + + # test with offset + assert_equal topics(:fourth), Topic.offset(1).second_to_last + assert_equal topics(:fourth), Topic.offset(2).second_to_last + assert_equal topics(:fourth), Topic.offset(3).second_to_last + assert_equal nil, Topic.offset(4).second_to_last + assert_equal nil, Topic.offset(5).second_to_last + + #test with limit + # assert_equal nil, Topic.limit(1).second # TODO: currently failing + assert_equal nil, Topic.limit(1).second_to_last + end + + def test_second_to_last_have_primary_key_order_by_default + expected = topics(:fourth) + expected.touch # PostgreSQL changes the default order if no order clause is used + assert_equal expected, Topic.second_to_last + end + + def test_model_class_responds_to_second_to_last_bang + assert Topic.second_to_last! + Topic.delete_all + assert_raises_with_message ActiveRecord::RecordNotFound, "Couldn't find Topic" do + Topic.second_to_last! + end + end + + def test_third_to_last + assert_equal topics(:third).title, Topic.third_to_last.title + + # test with offset + assert_equal topics(:third), Topic.offset(1).third_to_last + assert_equal topics(:third), Topic.offset(2).third_to_last + assert_equal nil, Topic.offset(3).third_to_last + assert_equal nil, Topic.offset(4).third_to_last + assert_equal nil, Topic.offset(5).third_to_last + + # test with limit + # assert_equal nil, Topic.limit(1).third # TODO: currently failing + assert_equal nil, Topic.limit(1).third_to_last + # assert_equal nil, Topic.limit(2).third # TODO: currently failing + assert_equal nil, Topic.limit(2).third_to_last + end + + def test_third_to_last_have_primary_key_order_by_default + expected = topics(:third) + expected.touch # PostgreSQL changes the default order if no order clause is used + assert_equal expected, Topic.third_to_last + end + + def test_model_class_responds_to_third_to_last_bang + assert Topic.third_to_last! + Topic.delete_all + assert_raises_with_message ActiveRecord::RecordNotFound, "Couldn't find Topic" do + Topic.third_to_last! + end + end + def test_last_bang_present assert_nothing_raised do assert_equal topics(:second), Topic.where("title = 'The Second Topic of the day'").last! |