From: Dominik Honnef <dominikho@...>
Date: 2008-02-18T03:34:43+09:00
Subject: Re: where to check for nils or empty?

On [Mon, 18.02.2008 01:29], Robert Klemme wrote:
> On 16.02.2008 19:32, John Honovich wrote:
>> I am processing arrays of URLs.  I call a series of methods to delete or
>> modify those urls. I have a risk that those methods will return an empty
>> or null array.
>>
>> I am trying to figure out where and how to best check if the array is
>> null or empty.
>>
>>
>> Right now, I am doing it like this:
>>
>> def process array
>>   array = firstReview array
>>   return if array.nil? || array.empty?
>>   array = secondReview array
>>   return if array.nil? || array.empty?
>>   # repeat again and again
>> end
>>
>> def firstReview array
>>   array.reject! {|a| @MasterList.include? (a)}
>> end
>>
>>
>> My approach works currently but feels ugly and repetitive.
>>
>> Any advice for improving this?
>
> There's a simple fix: do not assign to array.  You can then do
>
> first_review array and
>   second_review array and
>   third_review
>
> Or you do
>
> reviews = [
>   lambda {|ar| ar.reject! {|a| ...}},
>   lambda {|ar| ar.reject! {|a| ...}},
>   lambda {|ar| ar.reject! {|a| ...}},
>   lambda {|ar| ar.reject! {|a| ...}},
> ]
>
> def process array
>   reviews.all? {|rev| rev[array]}
> end
>
> Btw, if the return value of your review is actually to mean something  
> I'd rather define clear semantics aka "nil means terminate processing"  
> and make sure that your review methods return the proper value.  That's  
> easier than checking multiple conditions all the time (empty? or nil?).
>
> Kind regards
>
> 	robert


Your first approach won't work, as an empty array evaluates to true, 
but the processing should stop on empty arrays
-- 
Dominik Honnef