Mongoid.to_csv

Description

A simple Mongoid::Base to_csv() class method that preserves scopes. to_csv() returns the entire contents including the header ready to be written to file.

Usage

# Assuming a Movie model with title and director_id columns.
Movie.to_csv
# would return:
title,director_id
title,director_id
Black Swan,0
Inception,1
The Fighter,2
The King's Speech,3
The Kids Are All Right,4

Movie.bad.to_csv
# would return:
title,director_id
The Kids Are All Right,4

For normal arrays, ‘to_mongoid_csv` works the same way.

Movie.all.mongoid_to_csv
# Same as
Movie.to_csv

Why not Array.to_csv?

I tried.

require 'csv'
module ArrayToCSV
  def to_csv
    if first.is_a?(Mongoid::Document)
      MongoidToCSV.documents_to_csv(self)
    else
      super
    end
  end
end
Array.send :include, ArrayToCSV

Something is giving ruby’s internal ‘Array#to_csv` precedence and ignoring mine. Got tired of messing around with it.

Attribute#to_csv

After a model object’s attributes are collected, to_csv is called on the resulting array. However, this poses a problem because it will blindly convert the attributes to a string – i.e. call to_s on them. If one of your attributes is a Date, then calling to_s may produce unwanted output. For example, if you have Date::DATE_FORMATS = ‘%d %B, %Y’ your dates will have the month written out like ‘January’, ‘February’, etc. To counter this, this gem will make an attempt to call to_csv() on each attribute. To get YYYY-MM-DD output, you could do something like:

class Date
  def to_csv
    strftime('%Y-%m-%d')
  end
end

Note that object.send(attribute_name) is used, so datetime fields will be returned as ActiveSupport::TimeWithZone objects.

TODO

  • Options to specify columns to be included (currently, id and timestamp columns are excluded).

  • Combine with active_record_to_csv somehow since they are essentially doing the same thing.

Compatibility

Tested with Ruby 1.9.2-p318 and Mongoid v2.0.2

If you are using a lower version of Ruby 1.9.2-p318 (the p318 is important), you need to install and require the ‘faster_csv` gem. This was tested with faster_csv v1.5.4.

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