From 329ce1aa3e20bf42eea24e82d49bd22cf28f3825 Mon Sep 17 00:00:00 2001
From: jbranchaud <jbranchaud@gmail.com>
Date: Fri, 20 Mar 2026 09:18:10 -0500
Subject: [PATCH] Add Filter By Type as a Ruby TIL

---
 README.md              |  3 ++-
 ruby/filter-by-type.md | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 ruby/filter-by-type.md

diff --git a/README.md b/README.md
index 2715af4..4f15b6a 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ working across different projects via [VisualMode](https://www.visualmode.dev/).
 
 For a steady stream of TILs, [sign up for my newsletter](https://visualmode.kit.com/newsletter).
 
-_1760 TILs and counting..._
+_1761 TILs and counting..._
 
 See some of the other learning resources I work on:
 
@@ -1428,6 +1428,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [FactoryGirl Sequences](ruby/factory-girl-sequences.md)
 - [Fail](ruby/fail.md)
 - [Fetch Warns About Superseding Block Argument](ruby/fetch-warns-about-superseding-block-argument.md)
+- [Filter By Type](ruby/filter-by-type.md)
 - [Find The Min And Max With A Single Call](ruby/find-the-min-and-max-with-a-single-call.md)
 - [Finding The Source of Ruby Methods](ruby/finding-the-source-of-ruby-methods.md)
 - [Format A Hash Into A String Template](ruby/format-a-hash-into-a-string-template.md)
diff --git a/ruby/filter-by-type.md b/ruby/filter-by-type.md
new file mode 100644
index 0000000..578533d
--- /dev/null
+++ b/ruby/filter-by-type.md
@@ -0,0 +1,37 @@
+# Filter By Type
+
+In Ruby, we have several ways to check if something is a certain type (class or
+subclass). A couple common approaches you might see are `#is_a?` and `===`
+(case equality operator):
+
+```ruby
+> 3.is_a?(Integer)
+=> true
+> Integer === 3
+=> true
+> 3 === Integer
+=> false
+```
+
+Notice it is important to get the ordering of class and value right when using
+`===`.
+
+We can use these concepts to filter collections down to just those values of a
+certain type. We can also ditch those methods and instead use
+[`#grep`](https://ruby-doc.org/3.4.1/Enumerable.html#method-i-grep) to pattern
+match on the type directly.
+
+```ruby
+> nums = [1, :two, 3.0, 'four', 5, -> { 6 }, 0.7]
+=> [1, :two, 3.0, "four", 5, #<Proc:0x0000000123af0338 (irb):5 (lambda)>, 0.7]
+> nums.filter { it.is_a?(Numeric) }
+=> [1, 3.0, 5, 0.7]
+> nums.filter { Integer === it }
+=> [1, 5]
+> nums.grep(Integer)
+=> [1, 5]
+> nums.grep(Numeric)
+=> [1, 3.0, 5, 0.7]
+```
+
+[source](https://bsky.app/profile/lucianghinda.com/post/3mhi5xp3xhk25)