implement AR scopes

lib/kaminari.rb

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+require File.join(File.dirname(__FILE__), 'kaminari/railtie')

lib/kaminari/active_record.rb

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+module Kaminari
+  module ActiveRecord
+    extend ActiveSupport::Concern
+    PER_PAGE = 10
+
+    included do
+      def self.inherited(kls)
+        kls.class_eval do
+          # page(5)
+          scope :page, lambda {|num|
+            offset(PER_PAGE * ([num.to_i, 1].max - 1)).limit(PER_PAGE)
+          } do
+            # page(3).per(20)
+            def per(num)
+              offset(offset_value / limit_value * num).limit(num)
+            end
+
+            def num_pages
+              (except(:offset, :limit).count.to_f / limit_value).ceil
+            end
+
+            def current_page
+              (offset_value / limit_value) + 1
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/kaminari/railtie.rb

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+require 'rails'
+require 'active_record'
+require File.join(File.dirname(__FILE__), 'active_record')
+
+module Kaminari
+  class Railtie < ::Rails::Railtie
+    initializer 'paginatablize' do |app|
+      ::ActiveRecord::Base.send :include, Kaminari::ActiveRecord
+    end
+  end
+end

spec/models/scopes_spec.rb

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+require File.expand_path('../spec_helper', File.dirname(__FILE__))
+
+describe Kaminari::ActiveRecord do
+  before :all do
+    User.delete_all
+    1.upto(20) {|i| User.create! :name => "user#{'%02d' % i}" }
+  end
+
+  describe '#page' do
+    shared_examples_for 'the first page' do
+      it { should have(10).users }
+      its('first.name') { should == 'user01' }
+    end
+
+    shared_examples_for 'blank page' do
+      it { should have(0).users }
+    end
+
+    context 'page 1' do
+      subject { User.page 1 }
+      it_should_behave_like 'the first page'
+    end
+
+    context 'page 2' do
+      subject { User.page 2 }
+      it { should have(10).users }
+      its('first.name') { should == 'user11' }
+    end
+
+    context 'page without an argument' do
+      subject { User.page }
+      it_should_behave_like 'the first page'
+    end
+
+    context 'page < 1' do
+      subject { User.page 0 }
+      it_should_behave_like 'the first page'
+    end
+
+    context 'page > max page' do
+      subject { User.page 3 }
+      it_should_behave_like 'blank page'
+    end
+  end
+
+  describe '#per' do
+    context 'page 1 per 5' do
+      subject { User.page(1).per(5) }
+      it { should have(5).users }
+      its('first.name') { should == 'user01' }
+    end
+  end
+
+  describe '#num_pages' do
+    context 'per 10' do
+      subject { User.page.num_pages }
+      it { should == 2 }
+    end
+
+    context 'per 7' do
+      subject { User.page(2).per(7).num_pages }
+      it { should == 3 }
+    end
+
+    context 'per 65536' do
+      subject { User.page(50).per(65536).num_pages }
+      it { should == 1 }
+    end
+  end
+
+  describe '#current_page' do
+    context 'page 1' do
+      subject { User.page.current_page }
+      it { should == 1 }
+    end
+
+    context 'page 2' do
+      subject { User.page(2).per(3).current_page }
+      it { should == 2 }
+    end
+  end
+end