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4 files changed, 76 insertions, 0 deletions
diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md index a2a5da4afb..efaa6cd2a3 100644 --- a/activesupport/CHANGELOG.md +++ b/activesupport/CHANGELOG.md @@ -1,3 +1,8 @@ +* Add `Hash#transform_values` to simplify a common pattern where the values of a + hash must change, but the keys are left the same. + + *Sean Griffin* + * Always instrument `ActiveSupport::Cache`. Since `ActiveSupport::Notifications` only instrument items when there diff --git a/activesupport/lib/active_support/core_ext/hash.rb b/activesupport/lib/active_support/core_ext/hash.rb index f68e1662f9..af4d1da0eb 100644 --- a/activesupport/lib/active_support/core_ext/hash.rb +++ b/activesupport/lib/active_support/core_ext/hash.rb @@ -6,3 +6,4 @@ require 'active_support/core_ext/hash/indifferent_access' require 'active_support/core_ext/hash/keys' require 'active_support/core_ext/hash/reverse_merge' require 'active_support/core_ext/hash/slice' +require 'active_support/core_ext/hash/transform_values' diff --git a/activesupport/lib/active_support/core_ext/hash/transform_values.rb b/activesupport/lib/active_support/core_ext/hash/transform_values.rb new file mode 100644 index 0000000000..6ff7e91212 --- /dev/null +++ b/activesupport/lib/active_support/core_ext/hash/transform_values.rb @@ -0,0 +1,21 @@ +class Hash + # Returns a new hash with the results of running +block+ once for every value. + # The keys are unchanged. + # + # { a: 1, b: 2, c: 3 }.transform_values { |x| x * 2 } + # # => { a: 2, b: 4, c: 6 } + def transform_values(&block) + result = self.class.new + each do |key, value| + result[key] = yield(value) + end + result + end + + # Destructive +transform_values+ + def transform_values! + each do |key, value| + self[key] = yield(value) + end + end +end diff --git a/activesupport/test/core_ext/hash/transform_values_test.rb b/activesupport/test/core_ext/hash/transform_values_test.rb new file mode 100644 index 0000000000..4449c94701 --- /dev/null +++ b/activesupport/test/core_ext/hash/transform_values_test.rb @@ -0,0 +1,49 @@ +require 'abstract_unit' +require 'active_support/core_ext/hash/indifferent_access' +require 'active_support/core_ext/hash/transform_values' + +class TransformValuesTest < ActiveSupport::TestCase + test "transform_values returns a new hash with the values computed from the block" do + original = { a: 'a', b: 'b' } + mapped = original.transform_values { |v| v + '!' } + + assert_equal({ a: 'a', b: 'b' }, original) + assert_equal({ a: 'a!', b: 'b!' }, mapped) + end + + test "transform_values! modifies the values of the original" do + original = { a: 'a', b: 'b' } + mapped = original.transform_values! { |v| v + '!' } + + assert_equal({ a: 'a!', b: 'b!' }, original) + assert_same original, mapped + end + + test "indifferent access is still indifferent after mapping values" do + original = { a: 'a', b: 'b' }.with_indifferent_access + mapped = original.transform_values { |v| v + '!' } + + assert_equal 'a!', mapped[:a] + assert_equal 'a!', mapped['a'] + end + + # This is to be consistent with the behavior of Ruby's built in methods + # (e.g. #select, #reject) as of 2.2 + test "default values do not persist during mapping" do + original = Hash.new('foo') + original[:a] = 'a' + mapped = original.transform_values { |v| v + '!' } + + assert_equal 'a!', mapped[:a] + assert_nil mapped[:b] + end + + test "default procs do not persist after mapping" do + original = Hash.new { 'foo' } + original[:a] = 'a' + mapped = original.transform_values { |v| v + '!' } + + assert_equal 'a!', mapped[:a] + assert_nil mapped[:b] + end +end |