From: Robert Klemme <shortcutter@...>
Date: 2007-09-09T01:00:04+09:00
Subject: Re: #to_b - why isn't this one already in there?

On 08.09.2007 17:16, Logan Capaldo wrote:
> On 9/7/07, Giles Bowkett <gilesb@gmail.com> wrote:
>> everybody knows
>>
>> if "false"
>>
>> returns true. there are situations where that's a pain. I did a Rails
>> thing where I was creating objects and calling methods from options
>> hashes which I sometimes got by simply passing in params from a
>> controller and sometimes actually wrote as code. so I would have
>>
>> @some_boolean = options[:some_boolean]
>>
>> and five minutes later I'd be stubbing my metaphorical toe on an
>>
>> if "false"
>>
>> statement.
>>
>> so I changed it to this:
>>
>> @some_boolean = options[:some_boolean].to_b
>>
>> and implemented #to_b by doing this:
>>
>> class String
>>   def to_b
>>     case self
>>     when "true"
>>       true
>>     when "false"
>>       false
>>     else
>>       raise Exception
>>     end
>>   end
> 
>> at that point I could pass in options hashes and it didn't matter
>> whether they came in properly and correctly as actual boolean values
>> or blustered in the servants' entrance as URL parameters.
>>
> 
> This proposal, and the responses (the negative ones) I find
> interesting, because I think it highlights a "problem" with most of
> the #to_blah methods, especially on String.
> 
> If you can accept "32".to_i == 32 or "1.0".to_f == 1.0 (pretend for a
> moment theres no such thing as floating point inaccuracy ;) ) then it
> seems perfectly reasonable to accept "true".to_b == true. I think
> what's throwing people is that string doesn't need an additional
> method to be used in a boolean context, and they find the (if I may
> use the word) "cast" distasteful. the #to_blah methods aren't "cast"s
> they are conversions and so from that point of view I see nothing
> wrong with #to_b.

Yeah, but the problem to solve in this case is a bit different: we are 
talking about input parameter conversion which is IMHO an application 
specific thing.  For me that's at least part of the reason to *not* 
handle this by a general purpose conversion method.

> On the other hand, I think your implementation is
> flawed. #to_blah methods don't raise exceptions if they can give you
> some value. E.g.: "google".to_i #=> 0. It doesn't raise an exception.
> So I would pick one of (true, false) to be the result of
> "gooble".to_b.

Like this one?

class String
   def to_b() self != "false" end
end

Kind regards

	robert