From: Leslie Viljoen <leslie@...>
Date: 2005-08-13T00:57:52+09:00
Subject: Re: Array redefinition problem

david@vallner.net wrote:

>Cit�t Leslie Viljoen <leslie@camary.co.za>:
>
>  
>
>>Hello!
>>
>>I have a large program which needs to be able to use Postgres OR MySQL.
>>Since the MySQL module's query result has a num_rows method and Postgres
>>returns an array, I thought I'd just redefine Array like this:
>>
>>class Array
>> def num_rows
>>   return length
>> end
>>end
>>
>>But in another line (@entries = Array.new) I get:
>>
>>/var/www/ruby/core.rb:443:in `initialize': wrong number of arguments (0
>>for 2) (ArgumentError)
>>
>>Now if I do the same thing in a small test program, I get no errors.
>>This works:
>>
>>class Array
>>  def num_rows
>>    return length
>>  end
>>end
>>
>>res = Array.new
>>puts res.num_rows
>>
>>In the large program I am not redefining Array anywhere else - what else
>>can
>>cause this error?
>>
>>Les
>>
>>-- 
>>ruby -e "puts 'Just another fickle programmer'"
>>
>>Leslie Viljoen    [leslie@camary.co.za]
>>Camary Consulting [http://www.camary.co.za]
>>Cellphone         [083-6186100]
>>Personal web      [http://mobeus.homelinux.org]
>>
>>
>>
>>
>>    
>>
>
>
>If the Array redefinition is nested in a module, you are shadowing the builtin
>Array class with a locally defined one. Try:
>
>  class ::Array
>    # Redefine methods.
>  end
>
>to make sure you're redefining the builtin one.
>  
>

It's a web script, so I never noticed this warning in a class below the
array redef:
 warning: redefining Object#initialize may cause infinite loop

I had a "begin" in there that was unmatched, and a rescue several
functions later -
which was causing some real strange things.

Anyway, now that I have put the begin in the same function as the rescue,
I no longer get the error. But I still can't redefine Array - now I get:

/var/www/ruby/core.rb:22:in `num_rows': undefined local variable or
method `length' for #<#<Module:0xb65fcfec>::Array:0xb65e2c78> (NameError)

The first lines of the program are:
class ::Array
  def num_rows
    return length <--- LINE 22
  end
end

a = Array.new
puts a.num_rows     

-- so how do I access ::Array.length?

-- 
ruby -e "puts 'Just another fickle programmer'"

Leslie Viljoen    [leslie@camary.co.za]
Camary Consulting [http://www.camary.co.za]
Cellphone         [083-6186100]
Personal web      [http://mobeus.homelinux.org]