Merge pull request #67 from lpichler/extract_stable_sort_by

Extract method stable_sort_by

lib/more_core_extensions/all.rb

@@ -3,6 +3,7 @@
 require 'more_core_extensions/core_ext/array'
 require 'more_core_extensions/core_ext/benchmark'
 require 'more_core_extensions/core_ext/class'
+require 'more_core_extensions/core_ext/enumerable'
 require 'more_core_extensions/core_ext/hash'
 require 'more_core_extensions/core_ext/math'
 require 'more_core_extensions/core_ext/module'

lib/more_core_extensions/core_ext/enumerable.rb

@@ -0,0 +1 @@
+require 'more_core_extensions/core_ext/enumerable/sorting'

lib/more_core_extensions/core_ext/enumerable/sorting.rb

@@ -0,0 +1,39 @@
+module MoreCoreExtensions
+  module StableSorting
+    def self.included(klass)
+      klass.class_eval do
+        def stable_sort_by(col_names = nil, order = nil, &block)
+          # stabilizer is needed because of
+          # http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/170565
+          stabilizer = 0
+          nil_rows, sortable =
+              partition do |r|
+                Array(col_names).any? { |c| r[c].nil? }
+              end
+
+          data_array =
+              if col_names
+                sortable.sort_by do |r|
+                  stabilizer += 1
+                  [Array(col_names).map do |col|
+                    val = r[col]
+                    val = val.downcase if val.kind_of?(String)
+                    val = val.to_s     if val.kind_of?(FalseClass) || val.kind_of?(TrueClass)
+                    val
+                  end, stabilizer]
+                end
+              else
+                sortable.sort_by(&block)
+              end.to_a
+
+          data_array += nil_rows
+
+          data_array.reverse! if order == :descending
+          data_array
+        end
+      end
+    end
+  end
+end
+
+Enumerable.send(:include, MoreCoreExtensions::StableSorting)

spec/core_ext/enumerable/sorting_spec.rb

@@ -0,0 +1,65 @@
+describe Enumerator do
+  let(:unsorted_enumerable) do
+    [
+        {:id => :a, :int => 3, :string => "a", :bool => true},
+        {:id => :b, :int => 1, :string => "b", :bool => true},
+        {:id => :c, :int => 2, :string => "B", :bool => false},
+        {:id => :d, :int => 0, :string => "b", :bool => false},
+        {:id => :e, :int => 1, :string => "D", :bool => false},
+        {:id => :f, :int => 0, :string => "d", :bool => nil},
+        {:id => :g, :int => 1, :string => "E", :bool => true},
+        {:id => :h, :int => 2, :string => "e", :bool => true},
+    ].to_enum
+  end
+
+  let(:int_sorted_array) do
+    [
+        {:id => :d, :int => 0, :string => "b", :bool => false},
+        {:id => :f, :int => 0, :string => "d", :bool => nil},
+        {:id => :b, :int => 1, :string => "b", :bool => true},
+        {:id => :e, :int => 1, :string => "D", :bool => false},
+        {:id => :g, :int => 1, :string => "E", :bool => true},
+        {:id => :c, :int => 2, :string => "B", :bool => false},
+        {:id => :h, :int => 2, :string => "e", :bool => true},
+        {:id => :a, :int => 3, :string => "a", :bool => true},
+    ]
+  end
+
+  let(:string_sorted_array) do
+    [
+        {:id => :a, :int => 3, :string => "a", :bool => true},
+        {:id => :b, :int => 1, :string => "b", :bool => true},
+        {:id => :c, :int => 2, :string => "B", :bool => false},
+        {:id => :d, :int => 0, :string => "b", :bool => false},
+        {:id => :e, :int => 1, :string => "D", :bool => false},
+        {:id => :f, :int => 0, :string => "d", :bool => nil},
+        {:id => :g, :int => 1, :string => "E", :bool => true},
+        {:id => :h, :int => 2, :string => "e", :bool => true},
+    ]
+  end
+
+  let(:bool_sorted_array) do
+    [
+        {:id => :c, :int => 2, :string => "B", :bool => false},
+        {:id => :d, :int => 0, :string => "b", :bool => false},
+        {:id => :e, :int => 1, :string => "D", :bool => false},
+        {:id => :a, :int => 3, :string => "a", :bool => true},
+        {:id => :b, :int => 1, :string => "b", :bool => true},
+        {:id => :g, :int => 1, :string => "E", :bool => true},
+        {:id => :h, :int => 2, :string => "e", :bool => true},
+        {:id => :f, :int => 0, :string => "d", :bool => nil},
+    ]
+  end
+
+  it "sorts stable when order is ascending" do
+    expect(unsorted_enumerable.stable_sort_by([:int])).to eq(int_sorted_array)
+    expect(unsorted_enumerable.stable_sort_by([:string])).to eq(string_sorted_array)
+    expect(unsorted_enumerable.stable_sort_by([:bool])).to eq(bool_sorted_array)
+  end
+
+  it "sorts stable when order is descending" do
+    expect(unsorted_enumerable.stable_sort_by([:int], :descending)).to eq(int_sorted_array.reverse)
+    expect(unsorted_enumerable.stable_sort_by([:string], :descending)).to eq(string_sorted_array.reverse)
+    expect(unsorted_enumerable.stable_sort_by([:bool], :descending)).to eq(bool_sorted_array.reverse)
+  end
+end