Add Double Splat To Merge Hashes as a ruby til.

README.md

@@ -104,6 +104,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 - [Create an Array of Stringed Numbers](ruby/create-an-array-of-stringed-numbers.md)
 - [Destructuring Arrays In Blocks](ruby/destructuring-arrays-in-blocks.md)
 - [Disassemble Some Codes](ruby/disassemble-some-codes.md)
+- [Double Splat To Merge Hashes](ruby/double-splat-to-merge-hashes.md)
 - [Editing Code In Pry](ruby/editing-code-in-pry.md)
 - [Evaluating One-Off Commands](ruby/evaluating-one-off-commands.md)
 - [FactoryGirl Sequences](ruby/factory-girl-sequences.md)

ruby/double-splat-to-merge-hashes.md

@@ -0,0 +1,33 @@
+# Double Splat To Merge Hashes
+
+One way of merging two hashes is with `#merge`:
+
+```ruby
+> h1 = {a: 1, b: 2}
+=> {:a=>1, :b=>2}
+> h2 = {c: 3, d: 4}
+=> {:c=>3, :d=>4}
+> h1.merge(h2)
+=> {:a=>1, :b=>2, :c=>3, :d=>4}
+```
+
+You can also use double splats for a slightly more concise approach:
+
+```ruby
+> h1 = {a: 1, b: 2}
+=> {:a=>1, :b=>2}
+> h2 = {c: 3, d: 4}
+=> {:c=>3, :d=>4}
+> {**h1, **h2}
+=> {:a=>1, :b=>2, :c=>3, :d=>4}
+```
+
+This works particularly well when you want to expand an existing hash into a
+hash you are creating on the fly:
+
+```ruby
+> h1 = {a: 1, b: 2}
+=> {:a=>1, :b=>2}
+> {c: 3, d: 4, **h1}
+=> {:c=>3, :d=>4, :a=>1, :b=>2}
+```