Merge pull request #52 from lxneng/issue-50

let `object.next` and `object.previous` support specify a field

lib/by_star/orm/active_record/by_star.rb

@@ -55,13 +55,13 @@ def newest_query(options={})
     end
 
     def previous(options={})
-      field = self.class.by_star_start_field
+      field = self.class.by_star_start_field(options)
       value = self.send(field.split(".").last)
       self.class.by_star_scope(options.merge(scope_args: self)).where("#{field} < ?", value).reorder("#{field} DESC").first
     end
 
     def next(options={})
-      field = self.class.by_star_start_field
+      field = self.class.by_star_start_field(options)
       value = self.send(field.split(".").last)
       self.class.by_star_scope(options.merge(scope_args: self)).where("#{field} > ?", value).reorder("#{field} ASC").first
     end

lib/by_star/orm/mongoid/by_star.rb

@@ -61,12 +61,12 @@ def newest_query(options={})
     end
 
     def previous(options={})
-      field = self.class.by_star_start_field
+      field = self.class.by_star_start_field(options)
       self.class.by_star_scope(options.merge(scope_args: self)).lt(field => self.send(field)).reorder(field => :desc).first
     end
 
     def next(options={})
-      field = self.class.by_star_start_field
+      field = self.class.by_star_start_field(options)
       self.class.by_star_scope(options.merge(scope_args: self)).gt(field => self.send(field)).reorder(field => :asc).first
     end
   end

spec/fixtures/shared/seeds.rb

@@ -19,8 +19,8 @@
    2014-03-01
    2014-03-15
    2014-04-01
-   2014-04-15).map{|d| Time.zone.parse(d) + 17.hours }.each do |d|
-  Post.create!(:created_at => d, day_of_month: d.day)
+   2014-04-15).map{|d| Time.zone.parse(d) + 17.hours }.each_with_index do |d, index|
+  Post.create!(:created_at => d, :updated_at=> d + index.days, day_of_month: d.day)
   Appointment.create!(:created_at => d, day_of_month: d.day)
   Event.create!(:created_at => d, :start_time => d - 5.days, :end_time => d + 5.days, day_of_month: d.day)
 end

spec/integration/shared/by_direction.rb

@@ -149,5 +149,14 @@
       it{ expect(subject.next({ scope: ->{ where(day_of_month: 1) } }).created_at).to eq Time.zone.parse('2014-02-01 17:00:00') }
       it{ expect(subject.next({ scope: ->(record){ where(day_of_month: record.day_of_month - 4) } }).created_at).to eq Time.zone.parse('2014-02-01 17:00:00') }
     end
+
+    context 'specify a field' do
+      subject { Post.where(created_at: Time.zone.parse('2014-01-01 17:00:00')).first }
+      it{ expect(subject.previous.created_at).to eq Time.zone.parse('2013-12-31 17:00:00') }
+      it{ expect(subject.next.created_at).to eq Time.zone.parse('2014-01-05 17:00:00') }
+      it{ expect(subject.previous(field: 'updated_at').created_at).to eq Time.zone.parse('2013-12-31 17:00:00') }
+      it{ expect(subject.next(field: 'updated_at').created_at).to eq Time.zone.parse('2014-01-01 17:00:00') }
+    end
+
   end
 end