Add url_to_next_page and url_to_prev_page helper methods

closes #861

kaminari-core/lib/kaminari/helpers/helper_methods.rb

@@ -9,8 +9,9 @@ module Helpers
     #
     #   * <tt>url_for</tt>: A method that generates an actual path
     #   * <tt>params</tt>: A method that returns query string parameters
+    #   * <tt>request</tt>: A method that returns a Rack::Request object
     #
-    # A normal Rails controller implements both of the methods, which makes it
+    # A normal Rails controller implements all the methods, which makes it
     # trivial to use this module:
     #
     # ==== Examples
@@ -28,6 +29,36 @@ module Helpers
     #
     module UrlHelper
 
+      # A helper that calculates the url to the next page.
+      #
+      # ==== Examples
+      # Basic usage:
+      #
+      #   <%= next_page_url @items %>
+      #   #-> http://www.example.org/items?page=2
+      #
+      # It will return `nil` if there is no next page.
+      def next_page_url(scope, options = {})
+        "#{request.base_url}#{next_page_path(scope, options)}" if scope.next_page
+      end
+      alias path_to_next_url next_page_url
+
+      # A helper that calculates the url to the previous page.
+      #
+      # ==== Examples
+      # Basic usage:
+      #
+      #   <%= prev_page_url @items %>
+      #   #-> http://www.example.org/items
+      #
+      # It will return `nil` if there is no previous page.
+      def prev_page_url(scope, options = {})
+        "#{request.base_url}#{prev_page_path(scope, options)}" if scope.prev_page
+      end
+      alias previous_page_url     prev_page_url
+      alias url_to_prev_page      prev_page_url
+      alias url_to_previous_page  prev_page_url
+
       # A helper that calculates the path to the next page.
       #
       # ==== Examples

kaminari-core/test/helpers/action_view_extension_test.rb

@@ -536,5 +536,42 @@ def to_s
         assert_equal'/users?page=2', view.path_to_prev_page(users, params: {controller: 'users', action: 'index'})
       end
     end
+
+    sub_test_case '#next_page_url' do
+      setup do
+        2.times {|i| User.create! name: "user#{i}"}
+      end
+
+      test 'the first page' do
+        users = User.page(1).per(1)
+        assert_equal 'http://test.host/users?page=2', view.next_page_url(users, params: {controller: 'users', action: 'index'})
+      end
+
+      test 'the last page' do
+        users = User.page(2).per(1)
+        assert_nil view.next_page_url(users, params: {controller: 'users', action: 'index'})
+      end
+    end
+
+    sub_test_case '#prev_page_url' do
+      setup do
+        3.times {|i| User.create! name: "user#{i}"}
+      end
+
+      test 'the first page' do
+        users = User.page(1).per(1)
+        assert_nil view.prev_page_url(users, params: {controller: 'users', action: 'index'})
+      end
+
+      test 'the second page' do
+        users = User.page(2).per(1)
+        assert_equal 'http://test.host/users', view.prev_page_url(users, params: {controller: 'users', action: 'index'})
+      end
+
+      test 'the last page' do
+        users = User.page(3).per(1)
+        assert_equal'http://test.host/users?page=2', view.prev_page_url(users, params: {controller: 'users', action: 'index'})
+      end
+    end
   end
 end