Add in_groups to ActiveSupport::CoreExtensions::Array::Grouping. [#579 state:resolved]

Signed-off-by: Pratik Naik <pratiknaik@gmail.com>

3 files changed, 97 insertions, 6 deletions

diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index a7b33c09ad..8d3b136d80 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,11 @@
 *Edge*
 
+* Add Array#in_groups which splits or iterates over the array in specified number of groups. #579. [Adrian Mugnolo] Example:
+  
+  a = (1..10).to_a
+  a.in_groups(3)        #=> [[1, 2, 3, 4], [5, 6, 7, nil], [8, 9, 10, nil]]
+  a.in_groups(3, false) #=> [[1, 2, 3, 4], [5, 6, 7], [8, 9, 10]]
+
 * Fix TimeWithZone unmarshaling: coerce unmarshaled Time instances to utc, because Ruby's marshaling of Time instances doesn't respect the zone [Geoff Buesing]
 
 * Added Memoizable mixin for caching simple lazy loaded attributes [Josh Peek]
diff --git a/activesupport/lib/active_support/core_ext/array/grouping.rb b/activesupport/lib/active_support/core_ext/array/grouping.rb
index 767acc4e07..df37afb053 100644
--- a/activesupport/lib/active_support/core_ext/array/grouping.rb
+++ b/activesupport/lib/active_support/core_ext/array/grouping.rb
@@ -4,8 +4,8 @@ module ActiveSupport #:nodoc:
   module CoreExtensions #:nodoc:
     module Array #:nodoc:
       module Grouping
-        # Iterates over the array in groups of size +number+, padding any remaining 
-        # slots with +fill_with+ unless it is +false+.
+        # Splits or iterates over the array in groups of size +number+,
+        # padding any remaining slots with +fill_with+ unless it is +false+.
         # 
         #   %w(1 2 3 4 5 6 7).in_groups_of(3) {|g| p g}
         #   ["1", "2", "3"]
@@ -39,6 +39,49 @@ module ActiveSupport #:nodoc:
           end
         end
 
+        # Splits or iterates over the array in +number+ of groups, padding any
+        # remaining slots with +fill_with+ unless it is +false+.
+        #
+        #   %w(1 2 3 4 5 6 7 8 9 10).in_groups(3) {|g| p g}
+        #   ["1", "2", "3", "4"]
+        #   ["5", "6", "7", nil]
+        #   ["8", "9", "10", nil]
+        #
+        #   %w(1 2 3 4 5 6 7).in_groups(3, ' ') {|g| p g}
+        #   ["1", "2", "3"]
+        #   ["4", "5", " "]
+        #   ["6", "7", " "]
+        #
+        #   %w(1 2 3 4 5 6 7).in_groups(3, false) {|g| p g}
+        #   ["1", "2", "3"]
+        #   ["4", "5"]
+        #   ["6", "7"]
+        def in_groups(number, fill_with = nil)
+          # size / number gives minor group size;
+          # size % number gives how many objects need extra accomodation;
+          # each group hold either division or division + 1 items.
+          division = size / number
+          modulo = size % number
+
+          # create a new array avoiding dup
+          groups = []
+          start = 0
+
+          number.times do |index|
+            length = division + (modulo > 0 && modulo > index ? 1 : 0)
+            padding = fill_with != false &&
+              modulo > 0 && length == division ? 1 : 0
+            groups << slice(start, length).concat([fill_with] * padding)
+            start += length
+          end
+
+          if block_given?
+            groups.each{|g| yield(g) }
+          else
+            groups
+          end
+        end
+
         # Divides the array into one or more subarrays based on a delimiting +value+
         # or the result of an optional block.
         #
diff --git a/activesupport/test/core_ext/array_ext_test.rb b/activesupport/test/core_ext/array_ext_test.rb
index 7563be44f8..62a1f61d53 100644
--- a/activesupport/test/core_ext/array_ext_test.rb
+++ b/activesupport/test/core_ext/array_ext_test.rb
@@ -99,7 +99,7 @@ class ArrayExtToSTests < Test::Unit::TestCase
 end
 
 class ArrayExtGroupingTests < Test::Unit::TestCase
-  def test_group_by_with_perfect_fit
+  def test_in_groups_of_with_perfect_fit
     groups = []
     ('a'..'i').to_a.in_groups_of(3) do |group|
       groups << group
@@ -109,7 +109,7 @@ class ArrayExtGroupingTests < Test::Unit::TestCase
     assert_equal [%w(a b c), %w(d e f), %w(g h i)], ('a'..'i').to_a.in_groups_of(3)
   end
 
-  def test_group_by_with_padding
+  def test_in_groups_of_with_padding
     groups = []
     ('a'..'g').to_a.in_groups_of(3) do |group|
       groups << group
@@ -118,7 +118,7 @@ class ArrayExtGroupingTests < Test::Unit::TestCase
     assert_equal [%w(a b c), %w(d e f), ['g', nil, nil]], groups
   end
 
-  def test_group_by_pads_with_specified_values
+  def test_in_groups_of_pads_with_specified_values
     groups = []
 
     ('a'..'g').to_a.in_groups_of(3, 'foo') do |group|
@@ -128,7 +128,7 @@ class ArrayExtGroupingTests < Test::Unit::TestCase
     assert_equal [%w(a b c), %w(d e f), ['g', 'foo', 'foo']], groups
   end
 
-  def test_group_without_padding
+  def test_in_groups_of_without_padding
     groups = []
 
     ('a'..'g').to_a.in_groups_of(3, false) do |group|
@@ -137,6 +137,48 @@ class ArrayExtGroupingTests < Test::Unit::TestCase
 
     assert_equal [%w(a b c), %w(d e f), ['g']], groups
   end
+
+  def test_in_groups_returned_array_size
+    array = (1..7).to_a
+
+    1.upto(array.size + 1) do |number|
+      assert_equal number, array.in_groups(number).size
+    end
+  end
+
+  def test_in_groups_with_empty_array
+    assert_equal [[], [], []], [].in_groups(3)
+  end
+
+  def test_in_groups_with_block
+    array = (1..9).to_a
+    groups = []
+
+    array.in_groups(3) do |group|
+      groups << group
+    end
+
+    assert_equal array.in_groups(3), groups
+  end
+
+  def test_in_groups_with_perfect_fit
+    assert_equal [[1, 2, 3], [4, 5, 6], [7, 8, 9]],
+      (1..9).to_a.in_groups(3)
+  end
+
+  def test_in_groups_with_padding
+    array = (1..7).to_a
+
+    assert_equal [[1, 2, 3], [4, 5, nil], [6, 7, nil]],
+      array.in_groups(3)
+    assert_equal [[1, 2, 3], [4, 5, 'foo'], [6, 7, 'foo']],
+      array.in_groups(3, 'foo')
+  end
+
+  def test_in_groups_without_padding
+    assert_equal [[1, 2, 3], [4, 5], [6, 7]],
+      (1..7).to_a.in_groups(3, false)
+  end
 end
 
 class ArraySplitTests < Test::Unit::TestCase