From: Kristof Bastiaensen <kristof@...>
Date: 2004-04-29T20:54:14+09:00
Subject: Re: alias or alias_method problem

Hi,

On Thu, 29 Apr 2004 10:11:42 +0900, Angel Martin wrote:
>> > Try the following instead:
>> > 
>> > class Hash #hash[] === hash[nil]
>> >   alias_method "old_bracket_assign", "[]="
>> >   alias_method "old_bracket" ,"[]"
>> >   def []=(*ag)
>> >     value=ag.pop
>> >     return old_bracket_assign(nil, value) if ag.size<1
>> >     old_bracket_assign(*(ag.push(value)))
>> >   end
>> >   def [](*ag)
>> >     return old_bracket(nil) if ag.size<1
>> >     old_bracket(*ag)
>> >   end
>> > end
>> 
> Ok, works great but when i tried:
>   return _[]=(nil, value) if ag.size<1
> it protest with a aprox: "cannot assign to nil"

If you write _[]=(nil, value), ruby will interprete it
as:

(_)[] = (nil, value)
#meaning
(_).[]=((nil, value))

Which is invalid syntax, because (nil, value) as an expression 
is illegal. 
(The "cannot assign to nil" response is kind of a mystery to me...)

When written as:

_.[]=(nil, value) 

it will work, assuming _ contains something useful.

for example:

_ = {}
_.[]=(nil, 4)
_[nil]
=> 4

>   regards
>     Angel,

Hope this explanation helps.

Kristof