CSVision

Convert a Hash into a CSV the easy way.

Installation

Add this line to your application's Gemfile:

gem 'csvision'

And then execute:

bundle

Or install it yourself as:

gem install csvision

Usage

CSVision has no prerequisites other than ruby itself, which is pretty cool just include the csvision gem in your app and you'll be good to go.

Hash

CSVision adds to Hash the to_csv method, anything that inherits from Hash will inherit this method as well, you do not need to open Hash and include CSVision in it, just require the library in your code.

require 'csvision'
sample = { :name => 'foo', :last_name => 'bar', :age => 10 }
sample.to_csv #=> "\"last_name\",\"name\",\"age\"\n\"bar\",\"foo\",\"10\""

Rails

CSVision adds the following methods to Rails:

to_csv at the model instance
to_csv at the model class
add_csvision at the model class

A rails model might look something like this:

class Product < ActiveRecord::Base
  validates_presence_of :name, :permalink, :description
  add_csvision :except => %w/updated_at created_at/
end

CSVision lets you customize the way your CSV is formed, you can use any of the following options in the add_csvision method:

:only to set only those parameters you wish to include.
:except this does the opposite it excludes options from the list.
:delimeter this set the field delimeter and it defaults to "
:separator this set the field separator and it defults to ,

That's good and all but, you never want to just convert a single object to csv but collections instead, so imagine this model instead:

class User < ActiveRecord::Base
  add_csvision :csv_headers => %w/street_cred nickname incognito/, :body => lambda { |u| [ u.street_cred, u.nickname, u.incognito ] }

  scope :flunky, where( 'points <= 5' )

  def incognito
    nickname.reverse
  end

  def street_cred
    points * 100 + ( nickname_cred )
  end

  private
  def nickname_cred
    nickname.unpack( 'U' * nickname.length ).sum # good nickname equals more street cred
  end
end

You can use the :headers option to set your header names, and the :body option to specify the methods or properties from the option you want called in your csv, this gives you flexibility to choose how your csv is formed and from what it is formed, so this is an example of how this works.

5.times { |i| User.create( :nickname => "user#{ i * 3 }", :points => i * 5 ) }
puts User.to_csv

this will print:

"street_cred","nickname","incognito"
"495","user0","0resu"
"998","user3","3resu"
"1501","user6","6resu"
"2004","user9","9resu"
"2546","user12","21resu"

You can chain active record calls and even scopes in to your mix, so consider:

5.times { |i| User.create( :nickname => "user#{ i * 3 }", :points => i *5 ) }
puts User.flunky.to_csv

will print:

"street_cred","nickname","incognito"
"495","user0","0resu"
"998","user3","3resu"
"1501","user6","6resu"

Lastly, with the exception of :except and :only which will be ignore because you're setting the body manually all other option work:

5.times { |i| User.create( :nickname => "user#{ i * 3 }", :points => i *5 ) }
puts User.to_csv( :headers => false )

Will print:

"495","user0","0resu"
"998","user3","3resu"
"1501","user6","6resu"
"2004","user9","9resu"
"2546","user12","21resu"

Outside of Rails

Anything that inherits from Hash will respond_to? :to_csv however if you want to use this in any other regular class make sure you do the following:

Create a Hash attribute named attributes.
You'll need to have a class count and find_each methods if you want support for setting the body.
include CSVision in your class.

class SampleStack
  include CSVision
  attr_accessor :attributes, :count

  add_csvision :csv_headers => %w/price name/, :body => lambda { |s| [ s[:name], s[:price] ] }

  def initialize( attributes={}, inventory = [] )
    @attributes = attributes
    @@inventory = inventory
  end

  def self.count
    @@inventory.size
  end

  def self.find_each( opts={} )
    @@inventory.each do |item|
      yield item
    end
  end
end

After wards imagine the following:

sample_stack = SampleStack.new( :foo => 'foo', :bar => 'bar' )
puts sample_stack.to_csv

Will print:

"foo","bar"
"foo","bar"

But more importantly to_csv at the class level will:

inventory = [ { :name => 'beer', :price => 9 }, { :name => 'milk', :price => 5 }, { :name => 'tuna', :price => 3 } ]
sample_stack = SampleStack.new({ :name => 'groceries'}, inventory)
puts SampleStack.to_csv

Prints:

"price","name"
"beer","9"
"milk","5"
"tuna","3"

TODO:

Add support for other ORM's
Rails 3.x responder.

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Added some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request