log_switch

https://github.com/turboladen/log_switch

While developing other gems that needed a single class/singleton style logger, I got tired of repeating the code to create that logger and mix it in to my base class. I just wanted to require something, mix it in, and log:

MyThing.new.log "some message"

...and be able to switch that logging off programmatically:

MyThing.logging_enabled = false

This gem does that.

include LogSwitch to give your class a class-level logger and an instance-level #log method. Logging is off by default — turn it on explicitly:

require 'log_switch'

class MyThing
  include LogSwitch
end

MyThing.logging_enabled = true
MyThing.new.log "I like you, Ruby."
# => D, [2026-07-15T12:46:30.206465 #66434] DEBUG -- : <MyThing> I like you, Ruby.

Switch it back off and calls become no-ops:

MyThing.logging_enabled = false
MyThing.new.log "You're my favorite."   # => nothing is written

MyThing.logging_enabled = true          # ...and back on, for the examples below

Note the class name is prepended to each message. That is on by default.

The default level is :debug. Change it with default_log_level:

MyThing.default_log_level = :warn
MyThing.new.log "Crap!"
# => W, [2026-07-15T12:46:30.206563 #66434]  WARN -- : <MyThing> Crap!

Or pass a level per call:

MyThing.new.log "Stuff!", :info
# => I, [2026-07-15T12:46:30.206499 #66434]  INFO -- : <MyThing> Stuff!

The level is passed straight through to your Logger, so any method it responds to will do.

LogSwitch defaults to a Logger writing to STDOUT. Point it anywhere:

MyThing.logger = Logger.new('log.txt')
MyThing.new.log "hi!"

LogSwitch.logger sets the default for includers that have not set their own, and LogSwitch.reset_config! puts things back to a fresh STDOUT logger.

Anything responding to #each_line is logged one line per call, so a multi-line message stays readable:

MyThing.new.log "line one\nline two"
# => D, [...] DEBUG -- : <MyThing> line one
# => D, [...] DEBUG -- : <MyThing> line two

Objects that do not respond to #each_line (an Array, an Exception) are logged whole.

Pass a block to #log and it runs before the message is written — handy for one-off setup:

require 'fileutils'
log_directory = File.expand_path('log')

MyThing.new.log("Thanks brah!") do
  FileUtils.mkdir_p(log_directory)
end

For something that should run before every call, use before_log:

MyThing.before_log = proc { FileUtils.mkdir_p(log_directory) }
MyThing.new.log "Thanks brah!"    # runs the hook, then logs
MyThing.new.log "I'm hungry..."   # runs it again

• Ruby >= 3.3. Tested on 3.3, 3.4 and 4.0 (see .github/workflows/ci.yml).
• Runtime dependency: logger (no longer a default gem as of Ruby 4.0).

gem install log_switch

After checking out the source:

bundle install
bundle exec rake      # specs + RuboCop

I need to thank the savon project for most of the code here. Somehow I ran across how they do logging and started following suit. The code in log_switch is almost identical to Savon's logging.