Add Define Multiline Strings With Heredocs as a Ruby TIL

Author: jbranchaud

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).
 
-_1411 TILs and counting..._
+_1412 TILs and counting..._
 
 ---
 
@@ -1116,6 +1116,7 @@ _1411 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)
+- [Define Multiline Strings With Heredocs](ruby/define-multiline-strings-with-heredocs.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)

ruby/define-multiline-strings-with-heredocs.md

@@ -0,0 +1,47 @@
+# Define Multiline Strings With Heredocs
+
+[A _heredoc_ (_here document_) is a special ruby
+syntax](https://ruby-doc.org/core-2.5.0/doc/syntax/literals_rdoc.html#label-Here+Documents)
+for defining formatted multiline strings. These are useful for any situation
+where you need to define a block of text where newlines and indentation are
+preserved -- e.g. output an error, help message, or some formatted SQL.
+
+The standard syntax is defined with `<<` and some uppercase identifier (e.g.
+`TXT`, `DOC`, `SQL`, etc.) to open and close the multiline string.
+
+```ruby
+def lookup_team(team_id)
+  query = <<SQL
+    select users.id from users
+      join teams
+        on teams.id = users.team_id
+      where teams.id = #{team_id}
+      order by created_at desc
+      limit 10;
+SQL
+
+  team_member_ids = db.execute(query)
+end
+```
+
+With the SQL formatted this way, it is easier to read and we can print/log out
+this nicely formatted version to make debugging easier.
+
+Notice that the terminating `SQL` identifier is fully left justified. I find
+that visually off relative to the indentation of everything else, so I like to
+use the _indented_ heredoc syntax (`<<-`).
+
+```ruby
+def lookup_team(team_id)
+  query = <<-SQL
+    select users.id from users
+      join teams
+        on teams.id = users.team_id
+      where teams.id = #{team_id}
+      order by created_at desc
+      limit 10;
+  SQL
+
+  team_member_ids = db.execute(query)
+end
+```