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Debug Log

This is a simple RubyGem that provides a more convenient and powerful way of doing debug printouts than using puts or a logger directly.

Usage

Require the gem. If you are using Bundler, add this to your Gemfile:

gem 'debug_log', '~> version known to work'

Now you can do debug printouts like this:

my_list = [:a, :b, :c]
my_number = 5
debug.log("after variable initialization", "my_number", "my_list.size")

The first argument to the log method is a comment and the following arguments are Ruby expression that will be evaluated. Here is an example of what the output can look like:

DebugLog | after variable initialization | my_number="5" (Fixnum), my_list.size="3" (Fixnum) | /Users/peter/tmp/debug-example.rb:7:in `foo'

By default the logger will log to stdout, but you can change that through the configuration options:

DebugLog.logger = lambda { |message| Rails.logger.info(message) }
DebugLog.stdout = false # defaults to true
DebugLog.enabled = false # defaults to true

Credit

The approach to patching the binding object was taken from Niclas Nilssons presentation “The Ruby advantage - metaprogramming and DSLs” at Nordic Ruby 2010. Niclas has packaged up his own solution to debug printouts in his dp gem.