Add Format A Hash Into A String Template as a Ruby TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1399 TILs and counting..._
+_1400 TILs and counting..._
 
 ---
 
@@ -1129,6 +1129,7 @@ _1399 TILs and counting..._
 - [Fetch Warns About Superseding Block Argument](ruby/fetch-warns-about-superseding-block-argument.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)
 - [Generate A Signed JWT Token](ruby/generate-a-signed-jwt-token.md)
 - [Generate Ruby Version And Gemset Files With RVM](ruby/generate-ruby-version-and-gemset-files-with-rvm.md)
 - [Get Info About Your RubyGems Environment](ruby/get-info-about-your-ruby-gems-environment.md)

ruby/format-a-hash-into-a-string-template.md

@@ -0,0 +1,35 @@
+# Format A Hash Into A String Template
+
+The `%` method as defined by `String`
+([`String#%`](https://ruby-doc.org/core-3.0.0/String.html#method-i-25)) allows
+you to format (interpolate) an object or array of values into a string. That
+string needs to contain template markers for where the values should go.
+
+Here is an example of folding an array of values into a string with [`%s`
+format
+specifier](https://docs.ruby-lang.org/en/master/format_specifications_rdoc.html#label-Specifier+s):
+
+```ruby
+> User = Struct.new(:id)
+=> User
+> user1 = User.new(123)
+=> #<struct User id=123>
+> "%s ID: %s" % [user1.class.to_s, user1.id]
+=> "User ID: 123"
+```
+
+Or perhaps more usefully for a string that acts as a template, you can used
+named specifiers that correspond to hash keys:
+
+```ruby
+> template = "You paid %{formatted_price} for %{product}. Enjoy your purchase!"
+=> "You paid %{formatted_price} for %{product}. Enjoy your purchase!"
+
+> data = { product: "Ruby Explained™", formatted_price: "$38.99" }
+=> {:product=>"Ruby Explained™", :formatted_price=>"$38.99"}
+
+> template % data
+=> "You paid $38.99 for Ruby Explained™. Enjoy your purchase!"
+```
+
+[source](https://hashrocket.com/blog/posts/using-a-hash-of-data-for-string-replacement-in-ruby)