active_record_csv_importer.rb

require 'faster_csv'

class FasterCSV
  class Table
    def remove_blank_columns
      original_mode_method = "by_#{self.mode}!".to_sym
      by_col!.delete_if{|header, values| header.blank?}.send(original_mode_method)
    end
    
    def remove_blank_rows
      original_mode_method = "by_#{self.mode}!".to_sym
      by_row!.delete_if {|r| r.to_s.match(/^[\s\,]+$/)}.send(original_mode_method)
    end
  end
end

class ActiveRecordCsvImporter < TablelessActiveRecord
  attr_accessor :file, :ar_model
  attr_accessor :csv_table
  
  validates_presence_of :file, :ar_model, :message => 'is a required parameter'
  def validate
    parse_file
    validate_records if has_been_parsed?
  end
  
  def validate_records
    csv_table.each do |row|
      record = ar_model.new(row.to_hash)
      errors.add(row[0], record.errors.full_messages) if !record.valid?
    end
  end
  
  def parse_file
    begin
      csv = file.is_a?(String) ? File.open(file).read : file.read
      @csv_table = FasterCSV.parse(csv, :headers => true, :skip_blanks => true)
      @csv_table.remove_blank_columns
      @csv_table.remove_blank_rows
    rescue StandardError => e
      errors.add :file, "could not be parsed because #{e.message}"
    end
  end
  
  def has_been_parsed?
    csv_table && csv_table.is_a?(FasterCSV::Table)
  end
end

tableless_active_record.rb

class TablelessActiveRecord < ActiveRecord::Base
  def self.columns
    @columns ||= [];
  end

  def self.column(name, sql_type = nil, default = nil, null = true)
    columns << ActiveRecord::ConnectionAdapters::Column.new(name.to_s, default, sql_type.to_s, null)
  end

  # Override the save method to prevent exceptions.
  def save(validate = true)
    validate ? valid? : true
  end
end

translation_importer.rb

class TranslationImporter < ActiveRecordCsvImporter
  attr_accessor :locale

  validates_presence_of :locale, :message => 'is a required parameter'

  def validate_records
    csv_table.each do |row|
      record = ar_model.new(row.to_hash.merge(:locale => locale))
      errors.add(row[0], record.errors.full_messages) if !record.valid?
    end
  end

  def import!
    csv_table.each do |row|
      attrs = row.to_hash.merge(:locale => locale)
      Translation.update_or_create(attrs)
    end
  end

  def ar_model
    Translation
  end

end

translation_importer_controller.rb

class TranslationImporterController < ApplicationController
  def new
    @importer = TranslationImporter.new
  end

  def process_csv
    @importer = TranslationImporter.new(params[:importer])
    if @importer.valid?
      @importer.import!
      flash[:notice] = 'The translations have been imported!'
      redirect_to new_translation_importer_url
    else
      render :action => 'new'
    end
  end
end