Prevents raised exceptions to be computationally expensive. Reference: https://gist.github.com/olistik/46a0b2879d6b5e7f616a

application_controller.rb

class ApplicationController < ActionController::Base

  def index
    foo_data.foo1
    foo_data.foo2
    
    request.xxx
  end

  private

    def foo_data
      @foo_data ||= foo_data
    end

end

foo.rb

class Foo
  def initialize(name)
    @name = name
    log(:initialize)
  end

  def inspect
    log(:inspect)
  end

  def to_s
    log(:to_s)
  end

  def log(context)
    Rails.logger.debug "XXX Foo(#{@name}).#{context}"
  end
end

foo_data.rb

class FooData

  def inspect
    "this is a cheap string"
  end

  def foo1
    @foo1 ||= Foo.new(:foo1)
  end
  
  def foo2
    @foo2 ||= Foo.new(:foo2)
  end

end