Add Destructure The First Item From An Array as a Ruby til

Author: jbranchaud

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
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@@ -895,6 +895,7 @@ _1153 TILs and counting..._
 - [Defaulting To Frozen String Literals](ruby/defaulting-to-frozen-string-literals.md)
 - [Define A Custom RSpec Matcher](ruby/define-a-custom-rspec-matcher.md)
 - [Define A Method On A Struct](ruby/define-a-method-on-a-struct.md)
+- [Destructure The First Item From An Array](ruby/destructure-the-first-item-from-an-array.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)

ruby/destructure-the-first-item-from-an-array.md

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+# Destructure The First Item From An Array
+
+In true Ruby fashion, there are plenty of idomatic ways to get the first
+item from an array.
+
+One of the ways is with assignment destructuring of the array.
+
+It is common to see assignment destructuring with tuples:
+
+```ruby
+> name, email = ['Liz', '[email protected]']
+=> ["Liz", "[email protected]"]
+> name
+=> "Liz"
+> email
+=> "[email protected]"
+```
+
+If you only want the first element, try this:
+
+```ruby
+> name, *rest = ['Liz', '[email protected]']
+=> ["Liz", "[email protected]"]
+> name
+=> "Liz"
+> rest
+=> ["[email protected]"]
+```
+
+The first element is assigned to `name` and the remaining items in the array
+are assigned to `rest`. That's because of the `*`.
+
+I like to use this approach with an array-returning method.
+
+```ruby
+> def lookup_person(id)
+    ['Liz', '[email protected]', id]
+  end
+=> :lookup_person
+> name, *rest = lookup_person(22)
+=> ["Liz", "[email protected]", 22]
+> name
+=> "Liz"
+irb(main):013:0> rest
+=> ["[email protected]", 22]
+```
+
+This method works as expected when dealing with an empty array.
+
+```ruby
+> name, *rest = []
+=> []
+> name
+=> nil
+> rest
+=> []
+```
+
+In all of these, `, *rest` is important because otherwise the statement will be
+a standard variable assignment.