用ruby实例化Foo?[副本]

我该怎么做 instantiate bar.rb ?

# foo.rb
class Foo
  def initialize
    puts "foo"
  end
end

# bar.rb
require 'foo'

Foo.new

$ ruby bar.rb 
/home/thufir/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- foo (LoadError)
    from /home/thufir/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from bar.rb:2:in `<main>'

目前未使用模块。在以下情况下工作正常 Foo 在同一脚本中声明:

# bar.rb with Foo declared inside
class Foo
  def initialize
    puts "foo"
  end
end

Foo.new

$ ruby bar.rb 
foo