Array redefinition problem

L

Leslie Viljoen

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 [[email protected]]
Camary Consulting [http://www.camary.co.za]
Cellphone [083-6186100]
Personal web [http://mobeus.homelinux.org]
 
R

Robert Klemme

Leslie said:
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?
Click to expand...

My guess is that it's unrelated to your change of the Array class. Did
you check line 443 of core.rb?

robert
 
R

Reyn Vlietstra

heh, daars min afrikaaners op ruby-talk :)

Why dont you use one of the db wrappers, like dbi ?
Have you seen active_record ?

Hello!
=20
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:
=20
class Array
def num_rows
return length
end
end
=20
But in another line (@entries =3D Array.new) I get:
=20
/var/www/ruby/core.rb:443:in `initialize': wrong number of arguments (0
for 2) (ArgumentError)
=20
Now if I do the same thing in a small test program, I get no errors.
This works:
=20
class Array
def num_rows
return length
end
end
=20
res =3D Array.new
puts res.num_rows
=20
In the large program I am not redefining Array anywhere else - what else
can
cause this error?
=20
Les
=20
--
ruby -e "puts 'Just another fickle programmer'"
=20
Leslie Viljoen [[email protected]]
Camary Consulting [http://www.camary.co.za]
Cellphone [083-6186100]
Personal web [http://mobeus.homelinux.org]
=20
=20
=20
=20
Click to expand...


--=20
Reyn Vlietstra
 
L

Leslie Viljoen

Robert said:
Leslie Viljoen wrote:



My guess is that it's unrelated to your change of the Array class. Did
you check line 443 of core.rb?

robert
Click to expand...

line 443:

@entries = Array.new


When I take Array redefinition change out, the whole program runs fine, except
that it cannot call Array.num_rows, which is what I want.


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

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

Leslie Viljoen

Reyn said:
heh, daars min afrikaaners op ruby-talk :)
Click to expand...
heh. van waaraf is jy?
Why dont you use one of the db wrappers, like dbi ?
Have you seen active_record ?
Click to expand...
Hm, maybe a good idea. Although I do actually want to
solve this problem. Quite often with Ruby I get strange
errors and end up spending a lot of time commenting
large blocks of code out to try and narrow them dDoes anyone know of a
program that can underown.
My pet peeve is the "syntax error" on the last line of
code - meaning I have missed an "end" somewhere.
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 [[email protected]]
Camary Consulting [http://www.camary.co.za]
Cellphone [083-6186100]
Personal web [http://mobeus.homelinux.org]
Click to expand...
Click to expand...


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

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

David A. Black

Hi --

line 443:

@entries = Array.new


When I take Array redefinition change out, the whole program runs fine, except
that it cannot call Array.num_rows, which is what I want.
Click to expand...

I wonder whether there's another Array class, inside a module
namespace, or something like that. I can't really puzzle it out, but
the problem could, I think, lie in that direction. Or in some kind of
name clash introduced by a library you're require'ing, maybe.


David
 
D

david

Cit=E1t Leslie Viljoen said:
Hello!
=20
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 Postgre= s
returns an array, I thought I'd just redefine Array like this:
=20
class Array
def num_rows
return length
end
end
=20
But in another line (@entries =3D Array.new) I get:
=20
/var/www/ruby/core.rb:443:in `initialize': wrong number of arguments (0
for 2) (ArgumentError)
=20
Now if I do the same thing in a small test program, I get no errors.
This works:
=20
class Array
def num_rows
return length
end
end
=20
res =3D Array.new
puts res.num_rows
=20
In the large program I am not redefining Array anywhere else - what els= e
can
cause this error?
=20
Les
=20
--=20
ruby -e "puts 'Just another fickle programmer'"
=20
Leslie Viljoen [[email protected]]
Camary Consulting [http://www.camary.co.za]
Cellphone [083-6186100]
Personal web [http://mobeus.homelinux.org]
=20
=20
=20
=20
Click to expand...


If the Array redefinition is nested in a module, you are shadowing the bu=
iltin
Array class with a locally defined one. Try:

class ::Array
# Redefine methods.
end

to make sure you're redefining the builtin one.
 
D

david

Cit=E1t Leslie Viljoen said:
My pet peeve is the "syntax error" on the last line of
code - meaning I have missed an "end" somewhere.
Click to expand...

Religious indentation is your best friend, putting a comment next to an "=
end" to
signify what you're ending is another. Then have Emacs reindent the whole=
file
and finding the stray "end" shouldn't be difficult ;)

David Vallner
 
L

Leslie Viljoen

Cit=E1t Leslie Viljoen <[email protected]>:

=20
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 Postgre= s
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 =3D 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 =3D Array.new
puts res.num_rows

In the large program I am not redefining Array anywhere else - what els= e
can
cause this error?

Les

--=20
ruby -e "puts 'Just another fickle programmer'"

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




=20
Click to expand...


If the Array redefinition is nested in a module, you are shadowing the b= uiltin
Array class with a locally defined one. Try:

class ::Array
# Redefine methods.
end

to make sure you're redefining the builtin one.
=20
Click to expand...

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 =3D Array.new
puts a.num_rows =20

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

--=20
ruby -e "puts 'Just another fickle programmer'"

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

Brian Schröder

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
=20
I had a "begin" in there that was unmatched, and a rescue several
functions later -
which was causing some real strange things.
=20
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:
=20
/var/www/ruby/core.rb:22:in `num_rows': undefined local variable or
method `length' for #<#<Module:0xb65fcfec>::Array:0xb65e2c78> (NameError)
=20
The first lines of the program are:
class ::Array
def num_rows
return length <--- LINE 22
end
end
=20
a =3D Array.new
puts a.num_rows
=20
-- so how do I access ::Array.length?
Click to expand...

class Array
alias :num_rows :length=20
end

[1,2,3].num_rows #=3D> 3

--=20
http://ruby.brian-schroeder.de/

Stringed instrument chords: http://chordlist.brian-schroeder.de/
 
D

david

Cit=E1t Brian Schr=F6der said:
It's a web script, so I never noticed this warning in a class below t= he
array redef:
warning: redefining Object#initialize may cause infinite loop
=20
I had a "begin" in there that was unmatched, and a rescue several
functions later -
which was causing some real strange things.
=20
Anyway, now that I have put the begin in the same function as the res= cue,
I no longer get the error. But I still can't redefine Array - now I g= et:
=20
/var/www/ruby/core.rb:22:in `num_rows': undefined local variable or
method `length' for #<#<Module:0xb65fcfec>::Array:0xb65e2c78> (NameEr= ror)
=20
The first lines of the program are:
class ::Array
def num_rows
return length <--- LINE 22
end
end
=20
a =3D Array.new
puts a.num_rows
=20
-- so how do I access ::Array.length?
Click to expand...
=20
class Array
alias :num_rows :length=20
end
=20
[1,2,3].num_rows #=3D> 3
=20
--=20
http://ruby.brian-schroeder.de/
=20
Stringed instrument chords: http://chordlist.brian-schroeder.de/
=20
=20
Click to expand...

Yup, alias does indeed seem to be a better solution here. There might be =
a
slight bug with namespaces of methods implemented in C or something. Try =
using
explicitly self.length, if only for academic purposes?

David Vallner
 
D

david

Cit=E1t Leslie Viljoen said:
/var/www/ruby/core.rb:22:in `num_rows': undefined local variable or
method `length' for #<#<Module:0xb65fcfec>::Array:0xb65e2c78> (NameErro=
Click to expand...
r)

Ah wait, it seems whatever is running the web script is doing some voodoo=
with
namespaces - the global namespace isn't what it's supposed to be, in whic=
h case
not even the aliasing would work properly.

I'm possibly summoning the Daemon Obfuscatis here, but this should work n=
o
matter what:

[].class.class_eval {
alias_method:)num_rows, :length)
}

Feel free to confuse yourself by using module_eval, or define_method.

David Vallner
 
P

Pit Capitain

Leslie said:
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)
Click to expand...

You can see that you don't have an Array instance, but an instance of an
Array class in an anonymous module.
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?
Click to expand...

Maybe you can show us more of the code and more than the first line of
the stack backtrace.

Regards,
Pit
 

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