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

Define Multiline Strings With Heredocs

A heredoc (here document) is a special ruby syntax 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.

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 (<<-).

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