Forum: Ruby severe newbie question (class, fixnum, array)

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Colin Summers (Guest)
on 2007-06-14 23:26
(Received via mailing list)
I worked a lot in tcl, and this is my first day of trying something in
Ruby. Second, maybe.

class Thread
  def initialize number
    @number = number ; #
    @replies = 0 ;
  end ; # initialize

  def filename
    dirname = "./data/" ; # the directory where the files are kept
    filename = dirname + @number.toS + "-" + @replies.toS + ".html"
    return filename
  end ; # filename

end ; # Thread definition

puts "Finished definitions."

thread[1727] = Thread.new 1727

puts "The filename would be: "
puts thread[1727].filename


Of course, that doesn't work. It is unhappy with the code to create
the filename, since .toS is not a method for fixnum (which apparently
is what @number is, but I never TOLD it that was a fixnum).

And I can't seem to define "thread" to be an array of class Thread
objects. I want to refer to thread[1702] and thread[291] and hop
around like that.

(And, perhaps a more advanced question, right now I am making the
thread number part of the object, ultimately for a gorgeous bit of
code it seems like the object should just know the index of the array
instead, so if I ask thread[32] what it's filename is it would know
that it is thread #32. Can it do that?)

Thanks. I know it's a basic question. It's been a decade since I
learned a new language. I gotta get out more.

--Colin
1b6638227665b70097b803d6ed924a34?d=identicon&s=25 Nathan T. (shadowcipher)
on 2007-06-14 23:35
(Received via mailing list)
Perhaps you meant to write the following which would convert the number
to a
string?

@replies.to_s
Matthew Moss (Guest)
on 2007-06-14 23:41
(Received via mailing list)
> class Thread

I would say this is a bad idea, since I believe Thread is a core
class.  Call it MyThread, or ThreadDesc or something else.

>   def initialize number
>     @number = number ; #
>     @replies = 0 ;
>   end ; # initialize

Get rid of all the semicolons; they are usually not needed.

>   def filename
>     dirname = "./data/" ; # the directory where the files are kept
>     filename = dirname + @number.toS + "-" + @replies.toS + ".html"
>     return filename
>   end ; # filename

toS is not an existing method, but to_s is. Use that, or do this which
is more compact:

def filename
   "./data/#{@number}-#{@replies}.html"
end

Couple things here:
1. return is not necessary, as functions return the last evaluation.
2. #{ ... } within a string evaluates what is inside the curlies, and
embeds that in the string.


> thread[1727] = Thread.new 1727

You'll need to create the array first:
    thread = []
or
    thread = Array.new
Jerry Blanco (Guest)
on 2007-06-14 23:43
(Received via mailing list)
Three things:

a) it's to_s, as in @number.to_s
b) create the array and then insert an element to it:

thread = []
thread[1] = Thread.new 1

c) to create a file, you could (should?) use file.join, which will
create the path with the right separators, etc. Look for the rdoc for
File.join.
Florian Aßmann (Guest)
on 2007-06-14 23:54
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Hi Colin,

First of all: http://whytheluckystiff.net/ruby/pickaxe/

Am 14.06.2007 um 23:25 schrieb Colin Summers:

>    dirname = "./data/" ; # the directory where the files are kept
> puts "The filename would be: "
> puts thread[1727].filename
>
>
> Of course, that doesn't work. It is unhappy with the code to create
> the filename, since .toS is not a method for fixnum (which apparently
> is what @number is, but I never TOLD it that was a fixnum).
See: http://whytheluckystiff.net/ruby/pickaxe/html/tut_...
The method you probably search for is to_s...

>
> And I can't seem to define "thread" to be an array of class Thread
> objects. I want to refer to thread[1702] and thread[291] and hop
> around like that.
class Thread already exists and is, as its name foreshadows, for
http://whytheluckystiff.net/ruby/pickaxe/html/tut_...

>
> (And, perhaps a more advanced question, right now I am making the
> thread number part of the object, ultimately for a gorgeous bit of
> code it seems like the object should just know the index of the array
> instead, so if I ask thread[32] what it's filename is it would know
> that it is thread #32. Can it do that?)
class FileThread
   DIR = 'data'.freeze # defines class constant
   @@instances = Array.new # initializes class variable as array

   def self.new number # overwrites class method
     @@instances[number] ||= super # set array elem with result from
parent class if not already set
   end
   def self.[] number # defines new class method
     new number # class class method new
   end

   def initialize number
     @number = number
     @replies = 0
   end
   def filename
     # see http://whytheluckystiff.net/ruby/pickaxe/html/ref_...
     @filename ||= File.expand_path File.join( DIR, "#{ @number }-#
{ @replies }.html" )
   end
end

FileThread[1].filename # => "#{ Dir.getwd }/data/1-0.html"

Sincerely
Florian
Colin Summers (Guest)
on 2007-06-15 00:30
(Received via mailing list)
Ah, many thanks. Now it works. I should have thought about Thread
being a predefined class. I thought it highlighted like that because
it was a constant (what with the capital T I gave it).

Underbars are hard to keep in my head, I think in interCaps.

And the code Florian posted for the object to know it's index in an
array... I think that's probably too difficult for me at this point.
I'm still bumping around the first project I figured I could use Ruby
on.

Pickaxe is on my list for today's trip to the bookstore, and I'll poke
around in the first edition a little more. Chris Pine's guide is
awesome, I just wish he'd write part 2 through 10.

--Colin
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