Hierarchical logger

example.rb

# Let's see the logger in practice. Imagine, we want to
# perform some actions on each project assigned to a
# specific user (whose ID is in params[:id]).
logger. log ("Find user") do
  user = User.find (params [:id])
  logger.log("Found #{user.email]")
  
  logger.log("Iterate over projects") do
    user.projects.find_each do |project|
      logger.log(project.name) do
        # Do something with the project.
      end
    end
   end
end

# The code above would produce logs like:
#
# Find user
#   Found [email protected]
#   Iterating over projects
#     Acme
#     Manhattan

hierarchical_logger.rb

class HierarchicalLogger
  # io is an I0 object where logs will be printed.
  def initialize(io)
    @io = io
    # Level starts at 0, i.e. no indentation.
    @level = 0
  end
  
  def log(message)
    # First, log the message while taking the
    # current indentation level into account.
    @io.puts(" " * (level + message. to_s)
      
    # If no block is given then we're done.
    return if !block_given?
      
    # Otherwise, increase the indentation level
    @level += 1
      
    # ... run the block
    result = yield
      
    # ... and go back to the previous level.
    @level -= 1

    result
  end
end

source: https://twitter.com/gregnavis/status/1630191075070713858