module Roda::RodaPlugins::CaptureERB::InstanceMethods

def capture_erb(&block)

Restore the previous ERB output buffer before returning.
Return the value of the block, converted to a string.
with an empty string, and then yield to the block.
Temporarily replace the ERB output buffer 
def capture_erb(&block)
  outvar = render_opts[:template_opts][:outvar]
  buf_was = instance_variable_get(outvar)
  if buf_was.respond_to?(:capture) && !buf_was.instance_of?(String)
    buf_was.capture(&block)
  else
    begin
      instance_variable_set(outvar, String.new)
      yield.to_s
    ensure
      instance_variable_set(outvar, buf_was) if outvar && buf_was
    end
  end
end