1 files changed, 25 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/hash/reverse_merge.rb b/activesupport/lib/active_support/core_ext/hash/reverse_merge.rb
new file mode 100644
index 0000000000..ef8d592829
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/hash/reverse_merge.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class Hash
+  # Merges the caller into +other_hash+. For example,
+  #
+  #   options = options.reverse_merge(size: 25, velocity: 10)
+  #
+  # is equivalent to
+  #
+  #   options = { size: 25, velocity: 10 }.merge(options)
+  #
+  # This is particularly useful for initializing an options hash
+  # with default values.
+  def reverse_merge(other_hash)
+    other_hash.merge(self)
+  end
+  alias_method :with_defaults, :reverse_merge
+
+  # Destructive +reverse_merge+.
+  def reverse_merge!(other_hash)
+    replace(reverse_merge(other_hash))
+  end
+  alias_method :reverse_update, :reverse_merge!
+  alias_method :with_defaults!, :reverse_merge!
+end