Add Turning Things Into Hashes as a ruby til

Author: jbranchaud

README.md

@@ -10,7 +10,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 For a steady stream of TILs from a variety of rocketeers, checkout
 [til.hashrocket.com](https://til.hashrocket.com/).
 
-_820 TILs and counting..._
+_821 TILs and counting..._
 
 ---
 
@@ -674,6 +674,7 @@ _820 TILs and counting..._
 - [Squeeze Out The Extra Space](ruby/squeeze-out-the-extra-space.md)
 - [String Interpolation With Instance Variables](ruby/string-interpolation-with-instance-variables.md)
 - [Summing Collections](ruby/summing-collections.md)
+- [Turning Things Into Hashes](ruby/turning-things-into-hashes.md)
 - [Uncaught Exceptions In Pry](ruby/uncaught-exceptions-in-pry.md)
 - [`undef_method` And The Inheritance Hierarchy](ruby/undef-method-and-the-inheritance-hierarchy.md)
 - [Up And Down With Integers](ruby/up-and-down-with-integers.md)

ruby/turning-things-into-hashes.md

@@ -0,0 +1,48 @@
+# Turning Things Into Hashes
+
+We have `#to_h` for turning things into hashes.
+
+It works as an identity function:
+
+```ruby
+> {}.to_h
+=> {}
+> {hello: "world"}.to_h
+=> {:hello=>"world"}
+```
+
+It works with `nil`:
+
+```ruby
+> nil.to_h
+=> {}
+```
+
+Does it work with arrays?
+
+```ruby
+> [:one, 2].to_h
+TypeError: wrong element type Symbol at 0 (expected array)
+from (pry):36:in `to_h'
+```
+
+Yes, but only if it is an array of pairs:
+
+```ruby
+> [[:one, 2], [:three, 4]].to_h
+=> {:one=>2, :three=>4}
+```
+
+It also works with `Struct` and `OpenStruct`:
+
+```
+> Person = Struct.new(:name, :age)
+=> Person
+> bob = Person.new("bob", 45)
+=> #<struct Person name="bob", age=45>
+> bob.to_h
+=> {:name=>"bob", :age=>45}
+```
+
+You'll find that many other objects and gems support `#to_h` when it makes
+sense.