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From: Doug Jolley on 29 Jun 2010 17:53
> It's Ruby. You can always patch or alias_method_chain the target code
> if you're willing to bear some slight brittleness.

Good point. I've been considering whether I should re-think my position
that the underlying code is inaccessible. The truth is, the block of
data that I have in memory is actually a Rails layout. I was reluctant
to mention the Rails aspects in this forum. So, I don't know if I could
ever figure out what would need to be done; but, your idea is definitely
a good one. Thanks for the input.

... doug
--
Posted via http://www.ruby-forum.com/.

From: Ryan Davis on 29 Jun 2010 19:26

On Jun 29, 2010, at 14:20 , Tony Arcieri wrote:

> On Tue, Jun 29, 2010 at 11:50 AM, Doug Jolley <ddjolley(a)gmail.com> wrote:
>
>> Unfortunately that is precisely my case and that is precisely what I was
>> trying to avoid. (And, unfortunately, I don't have any control over the
>> target code.)
>
> It's Ruby. You can always patch or alias_method_chain the target code if
> you're willing to bear some slight brittleness.

That is EXACTLY what I was coming back to say... Tony beat me to it.


From: Robert Klemme on 30 Jun 2010 04:43
2010/6/29 Tony Arcieri <tony.arcieri(a)medioh.com>:
> On Tue, Jun 29, 2010 at 11:50 AM, Doug Jolley <ddjolley(a)gmail.com> wrote:
>
>> Unfortunately that is precisely my case and that is precisely what I was
>> trying to avoid.  (And, unfortunately, I don't have any control over the
>> target code.)
>
> It's Ruby.  You can always patch or alias_method_chain the target code if
> you're willing to bear some slight brittleness.

Is this always possible? Wouldn't you need some knowledge of the
inner workings of the target code? In this case for example, does it
open the file with File.open or maybe with File.foreach?

This is an interesting point of interface design: usually it is more
convenient to just pass a file name somewhere and that method opens
the file (or URL) and reads the data. But from a modularity point of
view it is generally better to pass an open IO like instance.

You can nicely layer this e.g.

class X
# convenience method that will open the file for you
def read_file(path)
File.open path |io|
read io
end
end

# yet another convenience method
def read_url(url)
...
end

# read the data
def read(io)
io.each_line do |line|
# whatever
end
end
end

The only drawback here is the additional method needed but convenience
comes at a price. :-)

Kind regards

robert

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

From: Brian Candler on 30 Jun 2010 08:53
Robert Klemme wrote:
>> It's Ruby. �You can always patch or alias_method_chain the target code if
>> you're willing to bear some slight brittleness.
>
> Is this always possible? Wouldn't you need some knowledge of the
> inner workings of the target code? In this case for example, does it
> open the file with File.open or maybe with File.foreach?

You simply find that part of the code, and replace the offending
method(s) with something else. In the limit, you replace everything with
your own code :-)

It would be convenient to be able to mock out File and Dir with a
virtual, in-RAM filesystem. I'm not aware of a library which does that,
but in principle I think it could be done.

> This is an interesting point of interface design: usually it is more
> convenient to just pass a file name somewhere and that method opens
> the file (or URL) and reads the data. But from a modularity point of
> view it is generally better to pass an open IO like instance.

Definitely. The original csv.rb in ruby 1.8 got this very badly wrong.

The new (faster_csv) interface is capable of this, but it suffers from
missing documentation. IIRR you have to do something like

FasterCSV.new($stdin).each do |row|
p row
end

Since the documented "primary" interface is
FasterCSV.foreach("path/to/file.csv"), you have to dig through the code
to work out how to handle an open stream.
--
Posted via http://www.ruby-forum.com/.

From: Robert Klemme on 30 Jun 2010 09:56
2010/6/30 Brian Candler <b.candler(a)pobox.com>:
> Robert Klemme wrote:
>>> It's Ruby. �You can always patch or alias_method_chain the target code if
>>> you're willing to bear some slight brittleness.
>>
>> Is this always possible?  Wouldn't you need some knowledge of the
>> inner workings of the target code?  In this case for example, does it
>> open the file with File.open or maybe with File.foreach?
>
> You simply find that part of the code, and replace the offending
> method(s) with something else. In the limit, you replace everything with
> your own code :-)

That's what I always wanted to do - seems I have to resurrect my
WorldDomination gem. :-)

> It would be convenient to be able to mock out File and Dir with a
> virtual, in-RAM filesystem. I'm not aware of a library which does that,
> but in principle I think it could be done.

Well, /tmp is in memory on many systems and writing a small file is
also a mostly in memory operation. Of course, this is not as cheap as
doing it completely in userland but probably sufficient for many
applications (although it's not really nice). At least one can use
Tempfile for this, e.g.

Tempfile "prefix", "/tmp" do |io|
io.write everything

io.seek 0
whatever_load_routine io
end

>> This is an interesting point of interface design: usually it is more
>> convenient to just pass a file name somewhere and that method opens
>> the file (or URL) and reads the data.  But from a modularity point of
>> view it is generally better to pass an open IO like instance.
>
> Definitely. The original csv.rb in ruby 1.8 got this very badly wrong.
>
> The new (faster_csv) interface is capable of this, but it suffers from
> missing documentation. IIRR you have to do something like
>
> FasterCSV.new($stdin).each do |row|
>  p row
> end
>
> Since the documented "primary" interface is
> FasterCSV.foreach("path/to/file.csv"), you have to dig through the code
> to work out how to handle an open stream.

Or have the idea to look at "ri CSV.new"...

Thanks for the hint. This is good to know.

Cheers

robert

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

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