The Embedded Ruby library is very useful for creating reusable template file for rendering data on forms, web pages and more.

You can use ERB for your own custom templates as well.

Usage

Create a template file for use, for example, __template.erb.txt. You will need to use the ERB syntax to enable the template to render data properly.

# __template.erb.txt

First Name:<%= first_name %>
Last Name:<%= last_name %>
PhoneNumber:<%= phone %>

Next you need to create the class containing the attributes (or methods) specified in the ERB file that will be used as the data source to render. In the above ERB these are first_name, last_name and phone.

class Person
  attr_accessor :first_name, :last_name, :phone

  TEMPLATE_FILE_PATH = "__template.erb.txt"

  def initialize(first_name, last_name, phone)
    @first_name = first_name
    @last_name = last_name
    @phone = phone
  end

  def render
    erb_template_file_path = File.join(TEMPLATE_FILE_PATH)

    erb = ERB.new(File.read(erb_template_file_path))

    erb.result(get_binding)
  end

  # disable:rubocop
  def get_binding
    binding
  end
end

ERB reaches into the class’s binding (i.e. get_binding) and calls the respective methods in order to acquire the values to render.

Example:

ng = Person.new("Nikolai", "Gogol")

File.open("out.txt") { |f| f.puts(ng.render))

This would create a new file out.txt which writes the resulting render for the ng object.

// out.txt

Hello Nikolai Gogol