Add Enumerable#pluck.

Allows fetching the same values from arrays as from ActiveRecord associations.

3 files changed, 20 insertions, 0 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 2fac308d2e..e77ebcb2f2 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   Add `Enumerable#pluck` to get the same values from arrays as from ActiveRecord
+    associations.
+
+    Fixes #20339.
+
+    *Kevin Deisz*
+
 *   Add a bang version to `ActiveSupport::OrderedOptions` get methods which will raise
     an `KeyError` if the value is `.blank?`
 
diff --git a/activesupport/lib/active_support/core_ext/enumerable.rb b/activesupport/lib/active_support/core_ext/enumerable.rb
index 7a893292b3..d28f26260e 100644
--- a/activesupport/lib/active_support/core_ext/enumerable.rb
+++ b/activesupport/lib/active_support/core_ext/enumerable.rb
@@ -71,6 +71,14 @@ module Enumerable
   def without(*elements)
     reject { |element| elements.include?(element) }
   end
+
+  # Convert an enumerable to an array based on the given key.
+  #
+  #   [{ name: "David" }, { name: "Rafael" }, { name: "Aaron" }].pluck(:name)
+  #     => ["David", "Rafael", "Aaron"]
+  def pluck(key)
+    map { |element| element[key] }
+  end
 end
 
 class Range #:nodoc:
diff --git a/activesupport/test/core_ext/enumerable_test.rb b/activesupport/test/core_ext/enumerable_test.rb
index e5d8ae7882..21743cdea5 100644
--- a/activesupport/test/core_ext/enumerable_test.rb
+++ b/activesupport/test/core_ext/enumerable_test.rb
@@ -110,4 +110,9 @@ class EnumerableTests < ActiveSupport::TestCase
     assert_equal [1, 2, 4], (1..5).to_set.without(3, 5)
     assert_equal({foo: 1, baz: 3}, {foo: 1, bar: 2, baz: 3}.without(:bar))
   end
+
+  def test_pluck
+    payments = GenericEnumerable.new([ Payment.new(5), Payment.new(15), Payment.new(10) ])
+    assert_equal [5, 15, 10], payments.pluck(:price)
+  end
 end