This content originally appeared on DEV Community and was authored by Oinak
I have recently shared A configuration system for ruby CLIs.
If you are designing a new ruby application or script, it is very possible that you wnt to write some logs to now what things ar heppening (or did happen) during the execution.
If you are using a large framework like Ruby on Rails thin might be solved for you, see Rails.logger.
But if you are building a small script or app you might be missing the conveninence of being able to call logger.info from anywhewre.
To this effect, I have a small module that cover the mos basic needs:
module Loggable
def self.included(base)
base.extend ClassMethods
end
def logger = self.class.logger
module ClassMethods
def log_to(logger) = @logger = logger
def logger = @logger ||= ::Logger.new($stdout)
end
end
You can include thi in any of your classes, and it gives you the essential interface.
class MyClass
include Loggable
def foo
logger.info "This is an informative message"
end
end
and then if you run
MyClass.new.foo
You will see:
I, [2025-07-14T15:20:25.814143 #6137] INFO -- : This is an informative message
In the standard output.
You can check Ruby Logger docs to see the underlying options.
Additionally, you have a class-level log_to method that you can call like this:
log_to custom_logger
To set up any specialised behavior. One such example is suppresing logging in tests:
# example using minitest/spec dsl
let(:logger) do
# ignore logger output except when testing it
Object.new.tap do |o|
def o.info(*); end
def o.error(*); end
end
end
before do
MyClass.log_to(logger)
end
This allows to inject a fake logger (or a double, or a mock or a spy...) without having Dependency Injection set up on every Logabble class initialize method.
If you know me you know I am very fond of tests, so of course here you have the test that goes with this module:
# minitest/spec DSL
describe Loggable do
let(:dummy_class) { Class.new { include Loggable } }
describe '.included' do
it 'extends ClassMethods' do
expect(dummy_class.singleton_class.included_modules).must_include Loggable::ClassMethods
end
end
describe '#logger' do
it 'returns the class logger' do
expect(dummy_class.new.logger).must_equal dummy_class.logger
end
end
describe Loggable::ClassMethods do
describe '.log_to' do
it 'sets the logger device' do
logger = Object.new
dummy_class.log_to(logger)
expect(dummy_class.logger).must_equal logger
end
end
describe '.logger' do
it 'defaults to a logger instance' do
expect(dummy_class.logger).must_be_instance_of Logger
end
end
end
end
I hope this is useful to you at some point, if it is, or you have a much better way, please let me know in the comments.
This content originally appeared on DEV Community and was authored by Oinak
Oinak | Sciencx (2025-07-14T13:37:23+00:00) Easy logging in your small ruby scripts/apps. Retrieved from https://www.scien.cx/2025/07/14/easy-logging-in-your-small-ruby-scripts-apps/
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