allow to pass Symbol or Proc into :limit option of #accepts_nested_attributes_for

activerecord/lib/active_record/nested_attributes.rb

@@ -245,7 +245,8 @@ module ClassMethods
       #   any value for _destroy.
       # [:limit]
       #   Allows you to specify the maximum number of the associated records that
-      #   can be processed with the nested attributes. If the size of the
+      #   can be processed with the nested attributes. Limit also can be specified as a
+      #   Proc or a Symbol pointing to a method that should return number. If the size of the
       #   nested attributes array exceeds the specified limit, NestedAttributes::TooManyRecords
       #   exception is raised. If omitted, any number associations can be processed.
       #   Note that the :limit option is only applicable to one-to-many associations.
@@ -388,8 +389,17 @@ def assign_nested_attributes_for_collection_association(association_name, attrib
         raise ArgumentError, "Hash or Array expected, got #{attributes_collection.class.name} (#{attributes_collection.inspect})"
       end
 
-      if options[:limit] && attributes_collection.size > options[:limit]
-        raise TooManyRecords, "Maximum #{options[:limit]} records are allowed. Got #{attributes_collection.size} records instead."
+      limit = case options[:limit]
+      when Symbol
+        send(options[:limit])
+      when Proc
+        options[:limit].call
+      else
+        options[:limit]
+      end
+
+      if limit && attributes_collection.size > limit
+        raise TooManyRecords, "Maximum #{limit} records are allowed. Got #{attributes_collection.size} records instead."
       end
 
       if attributes_collection.is_a? Hash

activerecord/test/cases/nested_attributes_test.rb

@@ -846,13 +846,7 @@ def setup
   include NestedAttributesOnACollectionAssociationTests
 end
 
-class TestNestedAttributesLimit < ActiveRecord::TestCase
-  def setup
-    Pirate.accepts_nested_attributes_for :parrots, :limit => 2
-
-    @pirate = Pirate.create!(:catchphrase => "Don' botharrr talkin' like one, savvy?")
-  end
-
+module NestedAttributesLimitTests
   def teardown
     Pirate.accepts_nested_attributes_for :parrots, :allow_destroy => true, :reject_if => proc { |attributes| attributes.empty? }
   end
@@ -876,6 +870,36 @@ def test_limit_with_exceeding_records
   end
 end
 
+class TestNestedAttributesLimitNumeric < ActiveRecord::TestCase
+  def setup
+    Pirate.accepts_nested_attributes_for :parrots, :limit => 2
+
+    @pirate = Pirate.create!(:catchphrase => "Don' botharrr talkin' like one, savvy?")
+  end
+
+  include NestedAttributesLimitTests
+end
+
+class TestNestedAttributesLimitSymbol < ActiveRecord::TestCase
+  def setup
+    Pirate.accepts_nested_attributes_for :parrots, :limit => :parrots_limit
+
+    @pirate = Pirate.create!(:catchphrase => "Don' botharrr talkin' like one, savvy?", :parrots_limit => 2)
+  end
+
+  include NestedAttributesLimitTests
+end
+
+class TestNestedAttributesLimitProc < ActiveRecord::TestCase
+  def setup
+    Pirate.accepts_nested_attributes_for :parrots, :limit => proc { 2 }
+
+    @pirate = Pirate.create!(:catchphrase => "Don' botharrr talkin' like one, savvy?")
+  end
+
+  include NestedAttributesLimitTests
+end
+
 class TestNestedAttributesWithNonStandardPrimaryKeys < ActiveRecord::TestCase
   fixtures :owners, :pets
 

activerecord/test/models/pirate.rb

@@ -53,7 +53,7 @@ def reject_empty_ships_on_create(attributes)
     attributes.delete('_reject_me_if_new').present? && !persisted?
   end
 
-  attr_accessor :cancel_save_from_callback
+  attr_accessor :cancel_save_from_callback, :parrots_limit
   before_save :cancel_save_callback_method, :if => :cancel_save_from_callback
   def cancel_save_callback_method
     false