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Override helpers in Rails

Sooner or later need to override some built in Rails helpers would occur. For example, I like to use number_to_currency helper to format prices in my application, but I want all prices to be formated in euros instead of dollars.

Worth noting is that you cannot simple redefine number_to_currency in application_helper.rb what would be the first thing on my mind to do. You can not redefine original helper method in ActionView::Base class as well. That is because helpers are included as mixin and methods from module are made available to class that includes the module, they are not copied, so if module methods are changed later so are the modules method in a class. Original helper method should be replaced in module where it comes from and in case of currencies this is ActionView::Helpers::NumberHelper.

Here is example that replaces original number_to_currency method and set default currency to Euro:

module ActionView
  module Helpers
    module NumberHelper
      def number_to_currency_with_euro(number, options = {})
        defaults = {:unit => ''}
        s = number_to_currency_without_euro(number, defaults.merge(options))
        s << ' &euro;' unless options[:unit]
      end
      alias_method_chain :number_to_currency, :euro
    end
  end
end

Working with dates in Ruby

Ruby has three classes for working with date and time: Date, DateTime which subclasses Date and Time. There is an interesting article why we need all 3 classes, and here are some notes about working with dates:

• Time.now != DateTime.now && Time.superclass != Date
• There is no method in Time class to convert object to a Date object, but you can write date = Date.new(time.year, time.mon, time.day). Rails extends DateTime and Time classes which allows to_date and to_time conversions for both classes.
• Today is Date.today and now it is Time.now, there is no such thing as Date.now but there is Time.today (even I didn’t saw it in RDocs)
• Tomorrow is Date.today+1, yestrday Date.today-1, to add or substract a month use Date.today >> 1 or Date.today << 1. See also Rails extensions to time class which allows to write things like Date.today.to_time.at_beginning_of_week
• Date class includes Comparable module which allows us to write some_date.between?(Date.today, Date.today + 7)
• Time.now.beginning_of_month.to_date.upto( Time.now.next_month.beginning_of_month.to_date-1) {|d| puts d.to_s} would print all days in current month in your Rails application.

Standard Ruby library also includes ParseDate library for parsing dates and returning array of values. Rails use ParseDate.parsedate to create dates so if you need to support input of additional date formats consider extending parsedate. I am not sure why Date.parse does not use ParseDate.parse but have its own implementation.

Creating PDF documents with tables in Ruby, Rails

I started to use Ruby FPDF to create PDF documents from our new Rails application MojGost.com. Ruby FPFD like it’s PHP counterpart does not have methods for creating tables. However, there are many examples and scripts available and that allowed me to quickly write small Ruby module which adds few methods for easy table creation.

• word wraping text in cells, based on width of columns
• page breaks on rows if table is too long

Download Fpdf::Table or see some examples below.

Example 1. simple table

require 'FPDF'
require 'fpdf/table'

class FPDF
  include Fpdf::Table
end

pdf = FPDF.new
pdf.AddPage
pdf.SetFont('helvetica','',10)
data = [
  ['100', 'lorem ipsum dorem'],
  ['100', 'lorem ipsum dorem'],
  ['100', 'lorem ipsum dorem'],
]
pdf.table(data)
pdf.Output('test_fpdf_table_1.pdf')

View Example 1 PDF

Example 2. width, word-wrap, aligment, page break

require 'FPDF'
require 'fpdf/table'

class FPDF
  include Fpdf::Table
end

pdf = FPDF.new
pdf.AddPage
pdf.SetFont('helvetica','',10)

data = []
30.times { |i| data << [i.to_s, '-', 'Lorem ipsum dolor sit' * 10] }

columns = [
  {:title => '#1', :aligment => 'R', :width => 20},  
  {:title => '#2', :width => 20},
  {:title => 'Text'}  
]

pdf.table(data, columns)
pdf.Output('test_fpdf_table_2.pdf')

View Example 2 PDF

Overriding class methods in Ruby

Class methods in Ruby are methods that work without being tied to any particular object (Java and PHP5 have static methods for similiar purpose). Class methods are distinguished from instance methods by placing the class name and a period in front of the method name. One thing that may not be obvious if you want to inherit class method is how to call equally named class method from parent class.

If you try to use super.class_method_name it would not work. That’s because class_method_name is class method and not instance method and as such it does not exists in object. Fortunately, classes in Ruby are objects too and you can interact with class like you interact with any other objects.

Enough talking, here is example:

class User
  def User.columns
    "name,email" 
  end
end

class Customer < User
  def Customer.columns
    self.superclass.columns + ",saldo" 
  end
end

puts Customer.columns # << name,email,saldo

Ruby / Rails alternative to PHP print_r() and var_dump()

Both PHP functions provides information about a variable passed as argument. It is often used in development to get quick and human-readable info about array or object. If you are using Rails you can use DebugHelper’s debug(object) helper function. Note that helpers are available only in views. In controllers, models and other Ruby code you can use ‘puts YAML::dump(object)’ method to get readable info about object.