From: Mike Moore <blowmage@...>
Date: 2011-03-04T03:27:29+09:00
Subject: Re: How to assign an element to a hash only if its value is not nil?

On Thu, Mar 3, 2011 at 10:55 AM, Robert Klemme
<shortcutter@googlemail.com> wrote:
> On 03.03.2011 18:38, Mike Moore wrote:
>>
>> On Thu, Mar 3, 2011 at 10:10 AM, Thomas W.<thomas@thomas-witt.com>  wrote:
>>>
>>> hash = {}
>>>    hash[:key] = myvalue
>>>
>>>
>>> How to assign hash[:key] only if myvalue is not nil?
>>>
>>> Current solution is:
>>>
>>>    hash[:key] = myvalue unless myvalue.nil?
>>>
>>>
>>> Is there something more beautiful?
>>
>> You could assign the all values and then remove the just the nil
>> values afterward.
>>
>>   >>  h = { :one =>  1, :two =>  2, :three =>  nil, :four =>  4, :five =>
>>  nil }
>>   =>  {:three=>nil, :four=>4, :five=>nil, :one=>1, :two=>2}
>>   >>  h[:six] = 6
>>   =>  6
>>   >>  h[:seven] = nil
>>   =>  nil
>>   >>  h.delete_if { |k, v| v.nil? }
>>   =>  {:four=>4, :six=>6, :one=>1, :two=>2}
>
> Oh, this is so ugly.  And also potentially inefficient since the hash table
> might grow larger than needed.

I disagree. I think removing nil values afterwards is nicer (more
beautiful?) than having the check on every single assignment. And this
isn't likely to be your bottleneck so trading a little inefficiency is
worthy of clearly communicating your intent, IMO.