From: Justin Collins <collinsj@...>
Date: 2006-04-14T02:57:08+09:00
Subject: Re: Question mark in attr_*

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Patrick Hurley wrote:
> On 4/13/06, Wiebe Cazemier <halfgaar@gmx.net> wrote:
>   
>> Hi,
>>
>> Methods which return booleans end with a question mark, by convention. But how
>> about boolean attributes (attr_[reader, accessor, writer])? Saying
>> "attr_reader :variable?" won't work. I find it rather strange when you have to
>> access boolean attributes without the question mark, but the methods with the
>> question mark.
>>
>>
>>
>>     
>
> As ruby does not have data types, the onus is on the developer to
> spell out that she/he wants such an accessor. So add this to your
> program:
>
> class Module
>  def battr_reader(sym, *more)
>    battr_reader(*more) unless more.empty?
>    define_method("#{sym}?") { !!instance_variable_get("@#{sym}") }
>  end
> end
>
> Then you can add a battr_reader to any class...
> pth
>
>   

This could be pretty handy...but I don't understand why you have the 
double negation?
>    define_method("#{sym}?") { !!instance_variable_get("@#{sym}") }

-Justin

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