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

I'm looking for a way to dump the structure of an object, similar to the PHP functions print_r and var_dump for debugging reasons.

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.

If you just want the relevant data to be displayed to stdout (the terminal output if you're running from the command line), you can use p some_object.

Prrevious answers are great but if you don't want to use the console (terminal), in Rails you can print the result in the View by using the debug's Helper ActionView::Helpers::DebugHelper

#app/view/controllers/post_controller.rb
def index
 @posts = Post.all
end

#app/view/posts/index.html.erb
<%= debug(@posts) %>

#start your server
rails -s

results (in browser)

- !ruby/object:Post
  raw_attributes:
    id: 2
    title: My Second Post
    body: Welcome!  This is another example post
    published_at: '2015-10-19 23:00:43.469520'
    created_at: '2015-10-20 00:00:43.470739'
    updated_at: '2015-10-20 00:00:43.470739'
  attributes: !ruby/object:ActiveRecord::AttributeSet
    attributes: !ruby/object:ActiveRecord::LazyAttributeHash
      types: &5
        id: &2 !ruby/object:ActiveRecord::Type::Integer
          precision: 
          scale: 
          limit: 
          range: !ruby/range
            begin: -2147483648
            end: 2147483648
            excl: true
        title: &3 !ruby/object:ActiveRecord::Type::String
          precision: 
          scale: 
          limit: 
        body: &4 !ruby/object:ActiveRecord::Type::Text
          precision: 
          scale: 
          limit: 
        published_at: !ruby/object:ActiveRecord::AttributeMethods::TimeZoneConversion::TimeZoneConverter
          subtype: &1 !ruby/object:ActiveRecord::Type::DateTime
            precision: 
            scale: 
            limit: 
        created_at: !ruby/object:ActiveRecord::AttributeMethods::TimeZoneConversion::TimeZoneConverter
          subtype: *1
        updated_at: !ruby/object:ActiveRecord::AttributeMethods::TimeZoneConversion::TimeZoneConverter
          subtype: *1

I use this :)

require 'yaml'

module AppHelpers
  module Debug
    module VarDump

      class << self

        def dump(dump_object, file_path)
          File.open file_path, "a+" do |log_file|
            current_date = Time.new.to_s + "\n" + YAML::dump(dump_object) + "\n"
            log_file.puts current_date
            log_file.close
          end
        end

      end

    end
  end
end

Lately I'm using awesome_print's ap method which works on the console as well as in views.

The type-specific colored output really makes a difference if you need to visually scan for String or Numeric objects (Although I had to tweak my stylesheet a little bit in order to get a polished look)

Recently I have become a fan of PRY, I've found it incredibly for doing things like inspecting variables, debugging running code and inspecting external code. It might be a little overkill as an answer to this specific question.