From 58e2b326fe99415794308ab57daa52fe0d0d0927 Mon Sep 17 00:00:00 2001
From: jbranchaud <jbranchaud@gmail.com>
Date: Wed, 10 Feb 2021 11:35:04 -0600
Subject: [PATCH] Add Exclude Values From An Array as a Ruby til

---
 README.md                            |  3 +-
 ruby/exclude-values-from-an-array.md | 41 ++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)
 create mode 100644 ruby/exclude-values-from-an-array.md

diff --git a/README.md b/README.md
index a65483a..d30b1a0 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://tinyletter.com/jbranchaud).
 
-_1041 TILs and counting..._
+_1042 TILs and counting..._
 
 ---
 
@@ -830,6 +830,7 @@ _1041 TILs and counting..._
 - [Encode A String As URL-Safe Base64](ruby/encode-a-string-as-url-safe-base64.md)
 - [Enumerate A Pairing Of Every Two Sequential Items](ruby/enumerate-a-pairing-of-every-two-sequential-items.md)
 - [Evaluating One-Off Commands](ruby/evaluating-one-off-commands.md)
+- [Exclude Values From An Array](ruby/exclude-values-from-an-array.md)
 - [Expect A Method To Be Called And Actually Call It](ruby/expect-a-method-to-be-called-and-actually-call-it.md)
 - [FactoryGirl Sequences](ruby/factory-girl-sequences.md)
 - [Fail](ruby/fail.md)
diff --git a/ruby/exclude-values-from-an-array.md b/ruby/exclude-values-from-an-array.md
new file mode 100644
index 0000000..908a04f
--- /dev/null
+++ b/ruby/exclude-values-from-an-array.md
@@ -0,0 +1,41 @@
+# Exclude Values From An Array
+
+In true Ruby fashion, there are all sorts of ways to exclude values from an
+array.
+
+If you just want to exclude `nil` values, you can use
+[`#compact`](https://ruby-doc.org/core-3.0.0/Array.html#method-i-compact).
+
+```ruby
+> [1,nil,:what,4].compact
+#=> [1, :what, 4]
+```
+
+If you want to exclude `nil` values and some other named value, you could use
+[`#filter`](https://ruby-doc.org/core-3.0.0/Array.html#method-i-filter) or
+[`#reject`](https://ruby-doc.org/core-3.0.0/Array.html#method-i-reject).
+
+```ruby
+> [1,nil,:what,4].filter { |val| !val.nil? && val != :what }
+#=> [1, 4]
+> [1,nil,:what,4].reject { |val| val.nil? || val == :what }
+#=> [1, 4]
+```
+
+The filter is clumsy and heavy-handed for this sort of example. A really terse
+way of doing the same thing is with set difference:
+[`#-`](https://ruby-doc.org/core-3.0.0/Array.html#method-i-2D).
+
+```ruby
+> [1,nil,:what,nil,5] - [:what,nil]
+#=> [1, 5]
+```
+
+Or the spelled out
+[`#difference`](https://ruby-doc.org/core-3.0.0/Array.html#method-i-difference)
+method.
+
+```ruby
+> [1,nil,:what,nil,5].difference([:what,nil])
+#=> [1, 5]
+```