Why does with_progress do "Thread.new"?

Question

This code sets gems in your project based on the gem manifest. Why is it necessary to create threads for this?

module Gemifest
  class Installer
    def initialize(gem)
      @gem = gem
    end

    def perform!
      begin
        $stdout = StringIO.new('')
        $stderr = StringIO.new('')
        with_progress 'Installing ' + @gem.name do
          `#{@gem_command} install --no-ri --no-rdoc #{@gem.line}`
        end
      ensure
        $stderr = STDERR
        $stdout = STDOUT
      end
    end

    private

    def with_progress(label)
      STDERR.print label
      begin
        t = Thread.new do
          loop do
            STDERR.print('.')
            STDERR.flush
            sleep 0.8
          end
        end
        yield
        STDERR.puts ' done!' unless $?.exitstatus > 0
      rescue => e
        STDOUT.puts "Error:"
        STDOUT.puts e.message
      ensure
        t.kill
      end
    end
  end
end

Answer 1

If you delete Thread.new, it yieldwill be executed after completion loop do ... end(i.e. never).

The goal of creating a loop in a separate thread is that it must be executed simultaneously with the block, and then be killed after the block is completed.