Retrieve members in a rank range

* Added `members_from_rank_range` and `members_from_rank_range_in` methods.
* Updated specs.

lib/leaderboard.rb

@@ -646,6 +646,52 @@ def members_from_score_range_in(leaderboard_name, minimum_score, maximum_score,
     end
   end
 
+  # Retrieve members from the leaderboard within a given rank range.
+  #
+  # @param starting_rank [int] Starting rank (inclusive).
+  # @param ending_rank [int] Ending rank (inclusive).
+  # @param options [Hash] Options to be used when retrieving the data from the leaderboard.
+  #
+  # @return members from the leaderboard that fall within the given rank range.
+  def members_from_rank_range(starting_rank, ending_rank, options = {})
+    members_from_rank_range_in(@leaderboard_name, starting_rank, ending_rank, options)
+  end
+
+  # Retrieve members from the named leaderboard within a given rank range.
+  #
+  # @param leaderboard_name [String] Name of the leaderboard.
+  # @param starting_rank [int] Starting rank (inclusive).
+  # @param ending_rank [int] Ending rank (inclusive).
+  # @param options [Hash] Options to be used when retrieving the data from the leaderboard.
+  #
+  # @return members from the leaderboard that fall within the given rank range.
+  def members_from_rank_range_in(leaderboard_name, starting_rank, ending_rank, options = {})
+    leaderboard_options = DEFAULT_LEADERBOARD_REQUEST_OPTIONS.dup
+    leaderboard_options.merge!(options)
+
+    starting_rank -= 1
+    if starting_rank < 0
+      starting_rank = 0
+    end
+
+    ending_rank -= 1
+    if ending_rank > total_members_in(leaderboard_name)
+      ending_rank = total_members_in(leaderboard_name) - 1
+    end
+
+    if @reverse
+      raw_leader_data = @redis_connection.zrange(leaderboard_name, starting_rank, ending_rank, :with_scores => false)
+    else
+      raw_leader_data = @redis_connection.zrevrange(leaderboard_name, starting_rank, ending_rank, :with_scores => false)
+    end
+
+    if raw_leader_data
+      return ranked_in_list_in(leaderboard_name, raw_leader_data, leaderboard_options)
+    else
+      return []
+    end
+  end
+
   # Retrieve a member at the specified index from the leaderboard.
   #
   # @param position [int] Position in leaderboard.

spec/leaderboard_spec.rb

@@ -618,4 +618,20 @@
     leaders[-1][:member].should eql('member_25')
     leaders[-1][:score].to_i.should be(25)
   end
+
+  it 'should allow you to retrieve a given set of members from the leaderboard in a rank range' do
+    rank_members_in_leaderboard(25)
+
+    members = @leaderboard.members_from_rank_range(5, 9)
+    members.size.should be(5)
+    members[0][:member].should eql('member_21')
+    members[0][:score].to_i.should be(21)    
+    members[4][:member].should eql('member_17')
+
+    members = @leaderboard.members_from_rank_range(-1, 26)
+    members.size.should be(25)
+    members[0][:member].should eql('member_25')
+    members[0][:score].to_i.should be(25)
+    members[24][:member].should eql('member_1')
+  end
 end

spec/reverse_leaderboard_spec.rb

@@ -334,4 +334,20 @@
     @leaderboard.total_members.should be(2)
     @leaderboard.leaders(1).first[:member].should eql('member_1')
   end
+
+  it 'should allow you to retrieve a given set of members from the leaderboard in a rank range' do
+    rank_members_in_leaderboard(25)
+
+    members = @leaderboard.members_from_rank_range(5, 9)
+    members.size.should be(5)
+    members[0][:member].should eql('member_5')
+    members[0][:score].to_i.should be(5)    
+    members[4][:member].should eql('member_9')
+
+    members = @leaderboard.members_from_rank_range(-1, 26)
+    members.size.should be(25)
+    members[0][:member].should eql('member_1')
+    members[0][:score].to_i.should be(1)    
+    members[24][:member].should eql('member_25')
+  end
 end