From: David Vallner <david@...>
Date: 2006-01-12T20:35:45+09:00
Subject: Re: [SPAM] safe array index ?

On Thu, 12 Jan 2006 12:08:05 +0100, Robert Klemme <bob.news@gmx.net> wrote:

> David Vallner wrote:
>> Phrogz wrote:
>>
>>> Christer Nilsson wrote:
>>>
>>>
>>>> class SafeArray < DelegateClass(Array)
>>>>  def [](index)
>>>>    fetch index
>>>>  end
>>>> end
>>>>
>>>>
>>>
>>> Or, even easier:
>>>
>>> class SafeArray < DelegateClass(Array)
>>>  alias_method :[], :fetch
>>> end
>>>
>>>
>> Groan at the different argument order of the alias statement and
>> #alias_method.
>
>>> class Foo
>>> def bar() "bar" end
>>> alias :b :bar
>>> end
> => nil
>>> Foo.new.b
> => "bar"
>>> class Bar
>>> def foo() "foo" end
>>> alias_method :f, :foo
>>> end
> => Bar
>>> Bar.new.f
> => "foo"
>
> It seems to me order is the same: first the new name then the old name.
> Am I missing something here?
>
> Kind regards
>
>     robert
>
>


My bad. However, it seems alias_method silently lets me use an undefined  
method name as the old name, which got me confused:

   irb(main):001:0> class Foo
   irb(main):002:1>   def bar
   irb(main):003:2>     puts "BAR"
   irb(main):004:2>   end
   irb(main):005:1>   alias :bar :bar1
   irb(main):006:1>   alias_method :bar, :bar2
   irb(main):007:1> end
   NameError: undefined method `bar1' for class `Foo'
           from (irb):5
   irb(main):008:0> Foo.new.bar
   BAR
   => nil
   irb(main):009:0> Foo.new.bar1
   NoMethodError: undefined method `bar1' for #<Foo:0x10295848>
           from (irb):9
   irb(main):010:0> Foo.new.bar2
   NoMethodError: undefined method `bar2' for #<Foo:0x102934f0>
           from (irb):10

David Vallner