From: Robert Klemme <shortcutter@...>
Date: 2009-08-14T16:02:35+09:00
Subject: Re: Simple If

2009/8/13 Robert Dober <robert.dober@gmail.com>:
> On Thu, Aug 13, 2009 at 5:00 PM, Robert
> Klemme<shortcutter@googlemail.com> wrote:
>> 2009/8/13 Robert Dober <robert.dober@gmail.com>:
>>> On Thu, Aug 13, 2009 at 10:18 AM, Anthony Eden<anthonyeden@gmail.com> wrote:
>>>> On Wed, Aug 12, 2009 at 10:14 PM, Pete Moran<pete@zoborg.com> wrote:
>>>>> UPDATE:
>>>>>
>>>>> This works
>>>>>
>>>>>    if params[:country][:id]
>>>>>      id = params[:country][:id]
>>>>>    else
>>>>>      id = params[:id]
>>>>>    end
>>>>>
>>>>> But is there a oneliner equivalent?
>>>>
>>>> id = params[:country][:id] || params[:id]
>>> maybe safer but still not safe
>>>
>>> id = params[:country] && params[:country][:id] || params[:id]
>>
>> I'd go for
>>
>> id = (params[:country] || params)[:id]
> that is nicely refactored
>>
>> But, this does not seem to be what OP needs.  The Perl code was
>>
>> my $id = (exists $hash->{id}) ? $hash->{id} : $_;
>>
>> For me that translates to something like this:
>>
>> def any_method(some_id_argument)
>>  id = @hash[:id] || some_id_argument
> not really, rather
>   id = @hash.fetch( :id, some_id_argument)

Good point!  Even though I brought up Hash#fetch in a recent thread I
forgot it this time.  Darn, my memory... :-)

> or the fancier
>   id = @hash.fetch( :id ){ some_id_argument }
>
> just for completeness ;) of the API. (This is interesting for some use
> cases as e.g. throwing an exception in the block, thus
>
> begin
>  @hash.fetch( :id )
> rescue KeyNotFoundIBelieve
>   raise OMGWhatDidYouDo
> end
>
> becomes
>
> @hash.fetch( :id ){ raise OMGWhatDidYouDo, "<b>AGAIN</b>" } ;)

If that should be general behavior then I'd do

@hash = Hash.new { raise OMGWhatDidYouDo, "<b>AGAIN</b>" }

elsewhere and then just

id = @hash[:id]

It depends on whether you want the same behavior for all misses or just some.

Cheers

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/