Rails - Dec 2007 - Strange Array behavior after upgrading to Rails 2.0.2

I''ve come around a strange problem, after upgrading to 2.0.2.

I have subclassed the Array class with this method to extract a random
item (I haven''t made it myself, but it is quite clever):

class Array
  def random(weights=nil)
    return random(map {|n| n.send(weights)}) if weights.is_a? Symbol

  puts length
  puts self

    weights ||= Array.new(length, 1.0)
    total = weights.inject(0.0) {|t,w| t+w}
    point = rand * total

    zip(weights).each do |n,w|
      return n if w >= point
      point -= w
    end
  end
end


If I use it with a simple array like:

arr = [5,8,7,3]
arr.random

It works fine.

But if i try the same with a database extraction I now get an error. As
an example, I have a model called "Banner":

banner_list = Banner.find(:all)
banner_list.random

This gives the following error:

--------------------------------
undefined method `*'' for #<Banner:0x489c3f4>
--------------------------------

The error occurs in the subclassing code at the following line:

point = rand * total

The strange thing is, that this has worked with Rails 1.2.5, but when
upgrading to 2.0.2, the error now occurs.

Does Rails 2.0.2 return results in another way than 1.2.5?
-- 
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Sorry I''ve made a slight typo (I was trying to find out what was 
happening...) The subclassing should look like this:

class Array
  def random(weights=nil)
    return random(map {|n| n.send(weights)}) if weights.is_a? Symbol

    weights ||= Array.new(length, 1.0)
    total = weights.inject(0.0) {|t,w| t+w}
    point = rand * total

    zip(weights).each do |n,w|
      return n if w >= point
      point -= w
    end
  end
end
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On Dec 28, 2007 10:48 AM, Carsten Gehling
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
> I''ve come around a strange problem, after upgrading to 2.0.2.
>
> I have subclassed the Array class with this method to extract a random
> item (I haven''t made it myself, but it is quite clever):
>
> class Array
>   def random(weights=nil)
>     return random(map {|n| n.send(weights)}) if weights.is_a? Symbol
>
>   puts length
>   puts self
>
>     weights ||= Array.new(length, 1.0)
>     total = weights.inject(0.0) {|t,w| t+w}
>     point = rand * total
>
>     zip(weights).each do |n,w|
>       return n if w >= point
>       point -= w
>     end
>   end
> end
>
>
> If I use it with a simple array like:
>
> arr = [5,8,7,3]
> arr.random
>
> It works fine.
>
> But if i try the same with a database extraction I now get an error. As
> an example, I have a model called "Banner":
>
> banner_list = Banner.find(:all)
> banner_list.random
>
> This gives the following error:
>
> --------------------------------
> undefined method `*'' for #<Banner:0x489c3f4>
ActiveSupport now adds an Array#rand method which returns a random
element, this overrides Kernel#rand which returns a float.

I think that changing the line

  point = rand * total

to

 point = Kernel::rand * total

will fix this.



-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/

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Rick Denatale wrote:
> I think that changing the line
> 
>   point = rand * total
> 
> to
> 
>  point = Kernel::rand * total
> 
> will fix this.
And indeed it did. Thank you very much! :-)

- Carsten

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On Dec 28, 12:56 pm, Carsten Gehling <rails-mailing-l...@andreas-
s.net> wrote:
> Rick Denatale wrote:
> > I think that changing the line
> >   point = rand * total
> > to
> >  point = Kernel::rand * total
> > will fix this.
>
> And indeed it did. Thank you very much! :-)
Couldn''t you just use Array#rand ?

///ark
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On Dec 28, 2007 4:27 PM, Mark Wilden
<mark-OCn100epQuBBDgjK7y7TUQ@public.gmane.org>
wrote:
>
> On Dec 28, 12:56pm, Carsten Gehling <rails-mailing-l...@andreas-
> s.net> wrote:
> > Rick Denatale wrote:
> > > I think that changing the line
> > > point = rand * total
> > > to
> > > point = Kernel::rand * total
> > > will fix this.
> >
> > And indeed it did. Thank you very much! :-)
>
> Couldn''t you just use Array#rand ?
I thought of suggesting that, but he''s trying to do something similar,
but with a parameter to provide a weighted distribution.  The rand
method in ActiveSupport only gives a uniform distribution.

It might be useful if this is only used with ActiveSupport to put something like

   return rand unless weightt

at the top of the method though.

-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/

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Rick Denatale wrote:
> I thought of suggesting that, but he''s trying to do something
similar,
> but with a parameter to provide a weighted distribution.  The rand
> method in ActiveSupport only gives a uniform distribution.
> 
> It might be useful if this is only used with ActiveSupport to put 
> something like
> 
>    return rand unless weightt
> 
> at the top of the method though.
You''re quite right Rick. The code could do with this refactoring, after
all it IS pre-2.0 :-) - thank you for your bright ideas.

I don''t recall who made this little nice function, but I think
I''ll
repost it on the net with modifications.

- Carsten
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