Is there a print_r or var_dump equivalent in Ruby / Ruby on Rails?

Question

The .inspect method of any object should format is correctly for display, just do..

<%= theobject.inspect %>

The .methods method may also be of use:

<%= theobject.methods.inspect %>

It may help to put that in <pre> tags, depending on the data

In views:

include DebugHelper

...your code...

debug(object)

In controllers, models, and other code:

puts YAML::dump(object)

Source

In a view you can use <%= debug(yourobject) %> which will generate a YAML view of your data. If you want something in your log you should use logger.debug yourobject.inspect.

You can also use YAML::dump shorthand (y) under Rails console:

>> y User.first
--- !ruby/object:User 
attributes: 
  created_at: 2009-05-24 20:16:11.099441
  updated_at: 2009-05-26 22:46:29.501245
  current_login_ip: 127.0.0.1
  id: "1"
  current_login_at: 2009-05-24 20:20:46.627254
  login_count: "1"
  last_login_ip: 
  last_login_at: 
  login: admin
attributes_cache: {}

=> nil
>> 

If you want to just preview some string contents, try using raise (for example in models, controllers or some other inaccessible place). You get the backtrace for free:)

>> raise Rails.root
RuntimeError: /home/marcin/work/github/project1
    from (irb):17
>> 

I also really encourage you to try ruby-debug:

• http://railscasts.com/episodes/54-debugging-with-ruby-debug
• http://www.sitepoint.com/article/debug-rails-app-ruby-debug/
• http://www.datanoise.com/articles/2006/7/12/tutorial-on-ruby-debug

It's incredibly helpful!

You can use puts some_variable.inspect. Or the shorter version: p some_variable. And for prettier output, you can use the awesome_print gem.