From: Benoit Daloze <eregontp@...>
Date: 2010-01-24T23:11:17+09:00
Subject: Re: Writing proper getter in a Ruby way

2010/1/24 Marnen Laibow-Koser <marnen@marnen.org>:
> This seems a strange use case, but in any event, ou should not be doing
> this much class checking.  I suggest a different approach entirely: pass
> a hash to the constructor rather like many Rails functions do.
>
> So:
>
> class Variable
>  attr.accessor :name, :proc
>  attr.writer :value
>
>  def initialize(options, &proc)
>    @name = options[:name] ? options[:name].to_s : nil
>    @value = options[:value]
>    @proc = proc
>  end
>
>>
>>   def value
>>     @value or @proc && @proc.call.value
>>   end
>>
>>   def to_s
>>     name || 'unnamed_variable'
>>   end
>> end
>
> ...and these can stay the same.
>

Thank you for your answer. I know that class checking is not so OO.
The old behavior was like you propose: using a Hash. and then we were using
@name, @value = options.values_at(:name, :value) # values_at is really
nice here :)

That's a very cool approach except it's really longer and I think it's
significant in this context.
We are writing a math library, this class represent a mathematical
variable, so here we have:

x = var :x, 3                                 # with my way
x = var name: :x, value: 3            # with hash, in 1.9
x = var :name => :x, :value => 3 # with hash, in 1.8 (not relevant)
To specify the name is already redundant with the real var name. It's
possible via caller to get it, with parsing, but that's not a very
good way neither. (Would you support that?)

So much checking in a case statement for classes looks bad, but it was
intended to raise an ArgumentError if we still used the old behavior.

So, could I have your opinion, if we forget about Hash because it
looks too long here ?
Thank you for your answer again.