Output Buffering with Ruby

advanced_output

A contents <<<
send this to a
this goes to a
a, I forgot to add this
<<<
B contents <<<
this goes to b
b, please
<<<

advanced_output_buffer.rb

a = OutputBuffer.new
b = OutputBuffer.new

a.activate
puts "send this to a"
puts "this goes to a"

b.activate
puts "this goes to b"
puts "b, please"

a.activate
puts "a, I forgot to add this"

OutputBuffer::restore_default

puts "A contents <<<\n#{a}<<<"
puts "B contents <<<\n#{b}<<<"

example.rake

namespace :example do

  desc "Some important task"
  task :notify, :send_email, :needs => [:environment] do |task, args|
    
    args.with_defaults(:send_email => false)
    
    buffer = OutputBuffer.new
    puts "this would ordinarily be displayed right away"
    buffer.stop
    
    if args[:send_email]
      # could send email here
      # UserMailer.deliver_notification_mail(buffer)
      puts "sending email <<<\n#{buffer}<<<"
    else
      puts buffer
    end
    
  end
 
end

output_buffer.rb

require "stringio"

class OutputBuffer
  
  def initialize
    @buffer = StringIO.new
    activate
  end
  
  def activate
    $stdout = @buffer
  end
  
  def to_s
    @buffer.rewind
    @buffer.read
  end
  
  def stop
    OutputBuffer::restore_default
  end
  
  def self.restore_default
    $stdout = STDOUT
  end
  
end

output_buffer_example.rb

require "stringio"

buffer = StringIO.new
$stdout = buffer

puts "this would ordinarily be displayed right away"

$stdout = STDOUT
buffer.rewind

puts "the buffer captured: #{buffer.read}"

# => the buffer captured: this would ordinarily be displayed right away

rake_output

$ rake example:notify
this would ordinarily be displayed right away

$ rake example:notify[true]
sending email <<<
this would ordinarily be displayed right away
<<<