Forum: Ruby newbie with a weird technical problem (@ least I think it's

Announcement (2017-05-07): www.ruby-forum.com is now read-only since I unfortunately do not have the time to support and maintain the forum any more. Please see rubyonrails.org/community and ruby-lang.org/en/community for other Rails- und Ruby-related community platforms.
will (Guest)
on 2006-12-27 15:38
(Received via mailing list)
Yep, as the post title implies, I'm a newbie.  Being a pragmatic newbie
I'd rather be learning to program, than searching for answers to
non-language acquisition questions/problems.  I'm pretty sure the
following falls in that latter group, so if it's in a manual somewhere
please tell me so _politely_ and point me to _the_ manual. :-)

I'm starting to go through Dave T.' Programming Ruby/Picaxe (I'm on
pgs 25-26 2nd edition if you care) and I'm using TextMate/Terminal to
code and run modified versions of the book's examples.  So I ran a
version of the following with a typographical error, which was apparent
with the Terminal feedback.  So far, so good.  I fixed the error and
tried to run it again.  The problem is that now when I run it, all I
get in response is a new blank prompt.  I've tried renaming the file,
the class, giving it a completely new set of variables in the array and
quiting/restarting the Terminal.  If I type the _exact_ same thing into
irb I'm able to create a book and book2 instance and .inspect each of
them.  But with the TextMate/Terminal combo = Nothing, nadda, zip!
HELP, PLEASE!


#filename bib.rb

class Book
  def initialize(title, author, pages)
    @title   = title
    @author  = author
    @pages   = pages
  end
end

book = Book.new("Ruby Tutorial", "Dave", 831)
book.inspect


#terminal results
computer: me$ ruby bib.rb
computer: me$
Timothy H. (Guest)
on 2006-12-27 15:46
(Received via mailing list)
will wrote:
> with the Terminal feedback.  So far, so good.  I fixed the error and
>
>
>
> #terminal results
> computer: me$ ruby bib.rb
> computer: me$
>
>
>

It's a language question. The inspect method returns a string. That
string is not automatically displayed on the terminal. You have to print
the string if you want to see it. Use "puts book.inspect" for example.

The reason you see the result in irb is that irb prints it for you.
Rimantas L. (Guest)
on 2006-12-27 15:46
(Received via mailing list)
> If I type the _exact_ same thing into
> irb I'm able to create a book and book2 instance and .inspect each of
> them.  But with the TextMate/Terminal combo = Nothing, nadda, zip!
> HELP, PLEASE!
<...>

> book = Book.new("Ruby Tutorial", "Dave", 831)
> book.inspect

It is because you do not output anything.
Change the last line to puts book.inspect


Regards,
Rimantas
Dick D. (Guest)
on 2006-12-27 15:48
(Received via mailing list)
On 27/12/06, will <removed_email_address@domain.invalid> wrote:


>     @title   = title
> computer: me$ ruby bib.rb
> computer: me$

The reason you see output in irb is that irb shows you what
the last statement evaluated to, like this:

rasputnik@hypnotoad:~$ irb
irb(main):001:0> 1
=> 1
irb(main):002:0> quit


Object#inspect returns a string, but you aren't doing anything with it!
irb is showing you the value of book.inspect as usual, but the script
version is less verbose.

try

puts book.inspect

and you'll see output from the non-irb version.
will (Guest)
on 2006-12-27 15:50
(Received via mailing list)
Thank you!  Your explanation helps me understand the subsequent
failures. Any idea why it 'almost' worked the first time?  (it printed
the @pages and @author info, and then it told me there was an error.)
Jason M. (Guest)
on 2006-12-27 15:52
(Received via mailing list)
On 12/27/06, will <removed_email_address@domain.invalid> wrote:
> version of the following with a typographical error, which was apparent
> #filename bib.rb
> book.inspect
>
>
> #terminal results
> computer: me$ ruby bib.rb
> computer: me$


I plugged that into SciTe and added this line to the end.
puts.book.inspect
I hit f5 and got this:
>ruby mailinglist.rb
#<Book:0x28ae894 @title="Ruby Tutorial", @pages=831, @author="Dave">
Jason M. (Guest)
on 2006-12-27 15:54
(Received via mailing list)
On 12/27/06, Jason M. <removed_email_address@domain.invalid> wrote:
> > pgs 25-26 2nd edition if you care) and I'm using TextMate/Terminal to
> >
> >
> puts.book.inspect
> I hit f5 and got this:
> >ruby mailinglist.rb
> #<Book:0x28ae894 @title="Ruby Tutorial", @pages=831, @author="Dave">
> >Exit code: 0
>

Err.  puts book.inspect as others pointed out :P
Morton G. (Guest)
on 2006-12-27 18:36
(Received via mailing list)
On Dec 27, 2006, at 8:37 AM, will wrote:

> ... I'm using TextMate/Terminal to
> code and run modified versions of the book's examples.

Since you're using TextMate (as I do), I recommend running Ruby code
from within TextMate. No need to bother with Terminal.

1. Use Bundles>Ruby>Run to run your script. Output goes to a RubyMate
window which will pop up.

2. Try the following:

   class Book
     def initialize(title, author, pages)
       @title   = title
       @author  = author
       @pages   = pages
     end
   end

   book = Book.new("Ruby Tutorial", "Dave", 831)
   book.inspect # =>

Note the '# =>' added to the last line. Choose Ruby>Evaluate and
Update '# =>' Markers from the Bundles menu. The last line will
change to

   book.inspect # => "#<Book:0x25454 @author=\"Dave\", @title=\"Ruby
Tutorial\", @pages=831>"

There are shortcuts for these bundle commands, and there are several
other aids to evaluating Ruby code built-in to the TextMate Ruby
bundle. I think you will find TextMate makes it easy to explore Ruby
without constantly switching back and forth to Terminal.

Regards, Morton
Gavin K. (Guest)
on 2006-12-27 18:50
(Received via mailing list)
will wrote:
> book = Book.new("Ruby Tutorial", "Dave", 831)
> book.inspect

Others have mentioned the need to output the value you are returning,
and have suggested:
  puts book.inspect
as a way to see that information. I just wanted to add the suggestion
that the 'p' method:
  p book
automatically calls #inspect on the object(s) passed, and then spits
them to stdout like puts does. (For comparison, the puts method calls
#to_s on the object(s) passed.) 'p' is very convenient when developing
and testing out your application, as the output sometimes gives you
more insight into the actual format of the data...particularly for
arrays:

  irb(main):001:0> a = [ 1, '2', [ '3 4', 5 ], 6 ]
  => [1, "2", ["3 4", 5], 6]

  irb(main):002:0> puts a
  1
  2
  3 4
  5
  6
  => nil

  irb(main):003:0> p a
  [1, "2", ["3 4", 5], 6]
  => nil

As you can see from that first line, it's the result of #inspect that
irb uses when outputting the result of the last command. (Both puts and
p return nil when finished, which is where those two "=> nil" lines
come from in irb.)
will (Guest)
on 2006-12-28 08:47
(Received via mailing list)
Thanks All!!!

Special thanks out to Morton and Phrogz for the extra, very handy,
tips!!

On 12/27/06, Phrogz <removed_email_address@domain.invalid> wrote:
>   p book
>   irb(main):002:0> puts a
>
> As you can see from that first line, it's the result of #inspect that
> irb uses when outputting the result of the last command. (Both puts and
> p return nil when finished, which is where those two "=> nil" lines
> come from in irb.)
>
>
>


--

watch it - http://www.videobomb.com/posts/show/7091
sign it - http://action.freepress.net/campaign/savethenet
save it - http://savetheinternet.com/
This topic is locked and can not be replied to.