Raise 'column_name undefined error' when column not present

When using enum for state column and enum config not set explicitly,
if column is not present in database then "NoMethodError: undefined
method 'type' for nil:NilClass" was raised for transitions which is
hard to debug.
Fix #152

lib/aasm/persistence/active_record_persistence.rb

@@ -96,7 +96,10 @@ module AASM
         end
 
         def aasm_column_looks_like_enum(name=:default)
-          self.class.columns_hash[self.class.aasm(name).attribute_name.to_s].type == :integer
+          column_name = self.class.aasm(name).attribute_name.to_s
+          column = self.class.columns_hash[column_name]
+          raise NoMethodError.new("undefined method '#{column_name}' for #{self.class}") if column.nil?
+          column.type == :integer
         end
 
         def aasm_guess_enum_method(name=:default)

spec/database.rb

@@ -1,5 +1,5 @@
 ActiveRecord::Migration.suppress_messages do
-  %w{gates multiple_gates readers writers transients simples no_scopes multiple_no_scopes no_direct_assignments multiple_no_direct_assignments thieves multiple_thieves localizer_test_models persisted_states provided_and_persisted_states with_enums with_true_enums with_false_enums false_states multiple_with_enums multiple_with_true_enums multiple_with_false_enums multiple_false_states readme_jobs}.each do |table_name|
+  %w{gates multiple_gates readers writers transients simples no_scopes multiple_no_scopes no_direct_assignments multiple_no_direct_assignments thieves multiple_thieves localizer_test_models persisted_states provided_and_persisted_states with_enums with_enum_without_columns multiple_with_enum_without_columns with_true_enums with_false_enums false_states multiple_with_enums multiple_with_true_enums multiple_with_false_enums multiple_false_states readme_jobs}.each do |table_name|
     ActiveRecord::Migration.create_table table_name, :force => true do |t|
       t.string "aasm_state"
     end

spec/models/active_record/with_enum_without_column.rb

@@ -0,0 +1,35 @@
+class WithEnumWithoutColumn < ActiveRecord::Base
+  include AASM
+
+  enum status: {
+    opened: 0,
+    closed: 1
+  }
+
+  aasm :column => :status do
+    state :closed, initial: true
+    state :opened
+
+    event :view do
+      transitions :to => :opened, :from => :closed
+    end
+  end
+end
+
+class MultipleWithEnumWithoutColumn < ActiveRecord::Base
+  include AASM
+
+  enum status: {
+    opened: 0,
+    closed: 1
+  }
+
+  aasm :left, :column => :status do
+    state :closed, initial: true
+    state :opened
+
+    event :view do
+      transitions :to => :opened, :from => :closed
+    end
+  end
+end

spec/unit/persistence/active_record_persistence_multiple_spec.rb

@@ -113,6 +113,17 @@ describe "instance methods" do
         end
       end
     end
+    
+    context "when AASM enum setting is not enabled and aasm column not present" do
+      before :each do
+        @multiple_with_enum_with_column = MultipleWithEnumWithoutColumn.new
+      end
+      
+      it "should raise NoMethodError for transitions" do
+        expect{@multiple_with_enum_with_column.send(:view, :left)}.to raise_error(NoMethodError, "undefined method 'status' for MultipleWithEnumWithoutColumn")  
+      end
+    end
+
   end
 
   context "when AASM is configured to use enum" do

spec/unit/persistence/active_record_persistence_spec.rb

@@ -113,6 +113,17 @@ describe "instance methods" do
         end
       end
     end
+
+    context "when AASM enum setting is not enabled and aasm column not present" do
+      before :each do
+        @with_enum_with_column = WithEnumWithoutColumn.new
+      end
+      
+      it "should raise NoMethodError for transitions" do
+        expect{@with_enum_with_column.send(:view)}.to raise_error(NoMethodError, "undefined method 'status' for WithEnumWithoutColumn")  
+      end
+    end
+
   end
 
   context "when AASM is configured to use enum" do