How do I print out the contents of an object in Rails for easy debugging?

I think I'm trying to get the PHP equivalent of print_r() (print human-readable); at present the raw output is:

ActiveRecord::Relation:0x10355d1c0

What should I do?

I generally first try .inspect, if that doesn't give me what I want, I'll switch to .to_yaml.

class User
  attr_accessor :name, :age
end

user = User.new
user.name = "John Smith"
user.age = 30

puts user.inspect
#=> #<User:0x423270c @name="John Smith", @age=30>
puts user.to_yaml
#=> --- !ruby/object:User
#=> age: 30
#=> name: John Smith

Hope that helps.

define the to_s method in your model. For example

class Person < ActiveRecord::Base
  def to_s
    "Name:#{self.name} Age:#{self.age} Weight: #{self.weight}"
  end
end

Then when you go to print it with #puts it will display that string with those variables.

I'm using the awesome_print gem

So you just have to type :

ap @var

In Rails you can print the result in the View by using the debug' 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

pp does the job too, no gem requiring is required.

@a = Accrual.first ; pp @a

#<Accrual:0x007ff521e5ba50
 id: 4,
 year: 2018,
 Jan: #<BigDecimal:7ff521e58f08,'0.11E2',9(27)>,
 Feb: #<BigDecimal:7ff521e585d0,'0.88E2',9(27)>,
 Mar: #<BigDecimal:7ff521e58030,'0.0',9(27)>,
 Apr: #<BigDecimal:7ff521e53698,'0.88E2',9(27)>,
 May: #<BigDecimal:7ff521e52fb8,'0.8E1',9(27)>,
 June: #<BigDecimal:7ff521e52900,'0.8E1',9(27)>,
 July: #<BigDecimal:7ff521e51ff0,'0.8E1',9(27)>,
 Aug: #<BigDecimal:7ff521e51bb8,'0.88E2',9(27)>,
 Sep: #<BigDecimal:7ff521e512f8,'0.88E2',9(27)>,
 Oct: #<BigDecimal:7ff521e506c8,'0.0',9(27)>,
 Nov: #<BigDecimal:7ff521e43d38,'0.888E3',9(27)>,
 Dec: #<BigDecimal:7ff521e43478,'0.0',9(27)>,

You can also print two instances of an object:

 pp( Accrual.first , Accrual.second)
`
`
`

inspect is great but sometimes not good enough. E.g. BigDecimal prints like this: #<BigDecimal:7ff49f5478b0,'0.1E2',9(18)>.

To have full control over what's printed you could redefine to_s or inspect methods. Or create your own one to not confuse future devs too much.

  class Something < ApplicationRecord

    def to_s
      attributes.map{ |k, v| { k => v.to_s } }.inject(:merge)
    end

  end

This will apply a method (i.e. to_s) to all attributes. This example will get rid of the ugly BigDecimals.

You can also redefine a handful of attributes only:

  def to_s
    attributes.merge({ my_attribute: my_attribute.to_s })
  end

You can also create a mix of the two or somehow add associations.

.inspect is what you're looking for, it's way easier IMO than .to_yaml!

user = User.new
user.name = "will"
user.email = "[email protected]"

user.inspect
#<name: "will", email: "[email protected]">

instance.attributes prints the whole hash inside rails console.

You need to use debug(@var). It's exactly like "print_r".