"paginates_per" is a declarative DSL to set default per_page value for each model

lib/kaminari/active_record.rb

@@ -1,7 +1,7 @@
 module Kaminari
   module ActiveRecord
     extend ActiveSupport::Concern
-    PER_PAGE = 25
+    DEFAULT_PER_PAGE = 25
 
     included do
       def self.inherited(kls)
@@ -12,10 +12,12 @@ module Kaminari
           end]
           kls.instance_variable_set('@inheritable_attributes', new_inheritable_attributes)
         end
+
         kls.class_eval do
           # page(5)
           scope :page, lambda {|num|
-            limit(PER_PAGE).offset(PER_PAGE * ([num.to_i, 1].max - 1))
+            per_page = @_default_per_page || Kaminari::ActiveRecord::DEFAULT_PER_PAGE
+            limit(per_page).offset(per_page * ([num.to_i, 1].max - 1))
           } do
             # page(3).per(10)
             def per(num)
@@ -30,6 +32,14 @@ module Kaminari
               (offset_value / limit_value) + 1
             end
           end
+
+          # overrides the default per_page value per model
+          #   class Article < ActiveRecord::Base
+          #     paginates_per 10
+          #   end
+          def self.paginates_per(val)
+            @_default_per_page = val
+          end
         end
       end
     end

spec/models/default_per_page_spec.rb

@@ -0,0 +1,15 @@
+require File.expand_path('../spec_helper', File.dirname(__FILE__))
+
+describe 'default per_page' do
+  subject { User.page 0 }
+
+  context 'by default' do
+    its(:limit_value) { should == 25 }
+  end
+
+  context 'when explicitly set via paginates_per' do
+    before { User.paginates_per 1326 }
+    its(:limit_value) { should == 1326 }
+    after { User.paginates_per nil }
+  end
+end