Severe newbie question (class, fixnum, array)


#1

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


#2

Perhaps you meant to write the following which would convert the number
to a
string?

@replies.to_s


#3

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


#4

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.


#5

Hi Colin,

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

Am 14.06.2007 um 23:25 schrieb Colin S.:

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_stdtypes.html
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_threads.html

(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_c_file.html
@filename ||= File.expand_path File.join( DIR, “#{ @number }-#
{ @replies }.html” )
end
end

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

Sincerely
Florian


#6

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 P.'s guide is
awesome, I just wish he’d write part 2 through 10.

–Colin