From: Robert Klemme <shortcutter@...>
Date: 2013-07-02T17:57:05+09:00
Subject: Re: including FileUtils::Verbose crashes Marshal.dump

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On Mon, Jul 1, 2013 at 6:40 PM, Joel VanderWerf <joelvanderwerf@gmail.com>wrote:

> On 07/01/2013 09:22 AM, Bryan Lockwood wrote:
> ...
>
>  My problem was that I read about fileutils in the pickaxe book (for 1.9
>> and 2.0), and the example included FileUtils::Verbose,
>> and I figured that would be fine for starters, as I could then see what
>> it was doing.
>>
>
> That example[1] seems to have been written with brevity in mind. It's ok
> in a 10 line script to include modules globally. In general, one must be
> careful, for reasons like the one you found. The internal state managed by
> those modules can interact badly with the internal state of other classes.
> It's better, though more verbose, to call methods on the module:
>
> FileUtils.cp(....)
>
> An exception would be if you were designing a class as a command language,
> like rake. But in that case, you would only include FileUtils into that
> class, not globally.
>

Even there I probably wouldn't.  Here's a shortened version of what happens:

$ ruby x.rb
[]
[:@var]
$ cat x.rb

module X
  def bar
    @var = 123
  end
end

include X

class Y
  def m
    bar
  end
end

y = Y.new
p y.instance_variables
y.m
p y.instance_variables
$

This shows the dangers of including modules.

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

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<div dir=3D"ltr"><br><div class=3D"gmail_extra"><br><br><div class=3D"gmail=
_quote">On Mon, Jul 1, 2013 at 6:40 PM, Joel VanderWerf <span dir=3D"ltr">&=
lt;<a href=3D"mailto:joelvanderwerf@gmail.com" target=3D"_blank">joelvander=
werf@gmail.com</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-=
left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;p=
adding-left:1ex">On 07/01/2013 09:22 AM, Bryan Lockwood wrote:<br>
...<div class=3D"im"><br>
<blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-=
left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;p=
adding-left:1ex">
My problem was that I read about fileutils in the pickaxe book (for 1.9 and=
 2.0), and the example included FileUtils::Verbose,<br>
and I figured that would be fine for starters, as I could then see what it =
was doing.<br>
</blockquote>
<br></div>
That example[1] seems to have been written with brevity in mind. It&#39;s o=
k in a 10 line script to include modules globally. In general, one must be =
careful, for reasons like the one you found. The internal state managed by =
those modules can interact badly with the internal state of other classes. =
It&#39;s better, though more verbose, to call methods on the module:<br>

<br>
FileUtils.cp(....)<br>
<br>
An exception would be if you were designing a class as a command language, =
like rake. But in that case, you would only include FileUtils into that cla=
ss, not globally.<br></blockquote><div><br></div><div style>Even there I pr=
obably wouldn&#39;t. =A0Here&#39;s a shortened version of what happens:</di=
v>
<div style><br></div><div style><div>$ ruby x.rb</div><div>[]</div><div>[:@=
var]</div><div>$ cat x.rb</div><div><br></div><div>module X</div><div>=A0 d=
ef bar</div><div>=A0 =A0 @var =3D 123</div><div>=A0 end</div><div>end</div>=
<div><br>
</div><div>include X</div><div><br></div><div>class Y</div><div>=A0 def m</=
div><div>=A0 =A0 bar</div><div>=A0 end</div><div>end</div><div><br></div><d=
iv>y =3D Y.new</div><div>p y.instance_variables</div><div>y.m</div><div>p y=
.instance_variables</div>
<div>$</div></div></div><div><br></div><div style>This shows the dangers of=
 including modules.</div><div style><br></div><div style>Kind regards</div>=
<div style><br></div><div style>robert</div><div><br></div>-- <br>remember.=
guy do |as, often| as.you_can - without end<br>
<a href=3D"http://blog.rubybestpractices.com/">http://blog.rubybestpractice=
s.com/</a>
</div></div>

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