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comp.lang.ruby

undefined local variable or method (filling an array

Thufir Hawat

11/10/2007 12:25:00 AM

I've been working on this for quite some time and don't understand the
error:


C:\code>
C:\code>type monsters.rb
require 'Dragon'
require 'ArrayOfCreaturesAttributes'
require 'CreatureAttributes'

monsters[0]=ArrayOfCreaturesAttributes.instance

C:\code>
C:\code>type ArrayOfCreaturesAttributes.rb
require 'singleton'
require 'Creature'
require 'CreatureAttributes'

class ArrayOfCreatureAttributes < Array

include Singleton


end
C:\code>
C:\code>type Creature.rb
require 'CreatureAttributes'

class Creature

Creature.extend CreatureAttributes
include CreatureAttributes


end
C:\code>


C:\code>
C:\code>monsters.rb
C:/code/monsters.rb:6: undefined local variable or method `monsters'
for main:Ob
ject (NameError)

C:\code>
4 Answers

7stud --

11/10/2007 12:43:00 AM

0

Thufir wrote:
> I've been working on this for quite some time and don't understand the
> error:
>
> C:/code/monsters.rb:6: undefined local variable or method `monsters'
> for main:Ob
> ject (NameError)
>

my_program.rb:

monsters[0] = 10

--output:--
undefined local variable or method `monsters' for main:Object
(NameError)

Normally, variables spring into existence when you assign to them.
However, the statement above works a little differently. The characters
'[]=' are actually the name of a method in the Array class. That means
the the code above is using the variable monsters to call that method.
However, in order to call a method of the Array class, you need an
existing array instance. But, nowhere in the code is an array
previously assign to the variable monsters.


Try this instead:

my_program.rb:

monsters = []
monsters[0] = 10
--
Posted via http://www.ruby-....

7stud --

11/10/2007 1:07:00 AM

0

7stud -- wrote:
> The characters
> '[]=' are actually the name of a method in the Array class.
>

To see that, you can also call the method '[]=' using the normal
variable.method_name syntax:

monsters = []
monsters.[]=(0, 10) #'[]=' is the name of a method

puts monsters[0]
--->10


--
Posted via http://www.ruby-....

Sebastian Hungerecker

11/10/2007 8:40:00 AM

0

7stud -- wrote:
> Try this instead:
> monsters = []
> monsters[0] = 10

Or this:
monsters = [10]


--
Jabber: sepp2k@jabber.org
ICQ: 205544826

Thufir Hawat

11/10/2007 8:57:00 PM

0

On Nov 9, 4:43 pm, 7stud -- <bbxx789_0...@yahoo.com> wrote:
> Thufir wrote:
> > I've been working on this for quite some time and don't understand the
> > error:
>
> > C:/code/monsters.rb:6: undefined local variable or method `monsters'
> > for main:Ob
> > ject (NameError)
>
> my_program.rb:
>
> monsters[0] = 10
>
> --output:--
> undefined local variable or method `monsters' for main:Object
> (NameError)
>
> Normally, variables spring into existence when you assign to them.
> However, the statement above works a little differently. The characters
> '[]=' are actually the name of a method in the Array class. That means
> the the code above is using the variable monsters to call that method.
> However, in order to call a method of the Array class, you need an
> existing array instance. But, nowhere in the code is an array
> previously assign to the variable monsters.
>
> Try this instead:
>
> my_program.rb:
>
> monsters = []
> monsters[0] = 10
> --
> Posted viahttp://www.ruby-....


Gee, it was so weird and frustrating. Thank you all!



-Thufir