Using annotate_models plugin

download or install annotate_models plugin (http://github.com/ganeshprasad/annotate_models) into vendor/plugins folder.
Now whenever you run the command rake annotate_models it will update the models with the schema.
Schema is also defined in ActiveRecord models whenever rake db:migrate is done.


Add a comment summarizing the current schema to the top or bottom of each of your…

* ActiveRecord models
  * Fixture files
  * Tests and Specs
  * Object Daddy exemplars
  * Machinist blueprints

The schema comment looks like this:

# == Schema Info
   #
   # Table name: line_items
   #
   #  id                  :integer(11)    not null, primary key
   #  quantity            :integer(11)    not null
   #  product_id          :integer(11)    not null
   #  unit_price          :float
   #  order_id            :integer(11)
   #

    class LineItem < ActiveRecord::Base
      belongs_to :product
     . . .

Reading huge csv or xls file and importing the data into database tables.

To implement this we need to gems fastercsv (gem install fastercsv) and ar-extensions ( gem install ar-extensions)

FasterCSV is intended as a replacement to Ruby‘s standard CSV library. It was designed to address concerns users of that library had and it has three primary goals:

1. Be significantly faster than CSV while remaining a pure Ruby library.
2. Use a smaller and easier to maintain code base. (FasterCSV is larger now, but considerably richer in features. The parsing core remains quite small.)
3. Improve on the CSV interface. 

Advantages:

• FasterCSV has a stricter parser and will throw MalformedCSVErrors on problematic data.
• FasterCSV has a less liberal idea of a line ending than CSV. What you set as the :row_sep is law.
• CSV returns empty lines as [nil]. FasterCSV calls them [].
• FasterCSV has a much faster parser. 

ar-extensions

ActiveRecord::Extensions provides extensions to:

• mass import data
• convert ActiveRecord models and arrays to CSV format
• work with temporary tables
• control foreign keys
• to include extensible features for better and custom finder support

Sample code to implement :
require 'rubygems'
require 'fastercsv'
require 'ar-extensions'
table_columns = [:attribute1,:attribute2, :attribute3, :attribute4, :attribute5 ]
table_data = Array.new


FasterCSV.foreach("#{RAILS_ROOT}/public/data/yourcsvfile.csv") do |row|
  row.delete_at(14)   #this can be used incase you want to delete any unnecessary column from any row of csv data

  table_data << row
end
options = { :validate => false }
CareHomeHq.import table_columns,table_data

Here insert of data will also be faster because we are not creating a new instance of CareHomeHq everytime a new row is fetched. Instead all the rows are saved in an array first and then we use ar-extensions to import the data.


PARSING FROM TEMP FILE
In case you want to parse from temp file then all you need to do is
  @parsed_file = FasterCSV.parse(params[:data_import][:file].read).each do |row|   
       puts row.inspect
      #your code here     
   end

Conditional validations in rails

By default, validations will take place every time the model is saved. Sometimes you only want a validation to happen when certain conditions are met. See how to do that in this episode.

# models/user.rb
validates_presence_of :password, :if => :should_validate_password?
validates_presence_of :country
validates_presence_of :state, :if => :in_us?
attr_accessor :updating_password

def in_us?
 country == 'US'
end

def should_validate_password?
 updating_password || new_record?
end

# in controller
@user.updating_password = true
@user.save

# or...
@user.save(false)