From: Mike Moore <blowmage@...>
Date: 2011-03-05T00:20:38+09:00
Subject: Re: How to assign an element to a hash only if its value is not nil?

On Fri, Mar 4, 2011 at 3:05 AM, Robert Klemme
<shortcutter@googlemail.com> wrote:
>
> If you want to clearly communicate the intent you can add a comment or
> an assert statement to that effect.  First inserting something that is
> removed later is totally backwards.

I'm sure there are cases where removing values from a hash is appropriate.

> Plus, you might remove more than
> intended, e.g. if there are nil values inserted previously and you
> only want to avoid inserting nils during _this_ method call.

In that case where you don't want to remove all nil values from a hash
you shouldn't call `delete_if { |k, v| v.nil? }`

> So, your
> proposed solution is less efficient and error prone.  Now how is that
> beautiful?

Ouch. So its ugly *AND* buggy...

  # Check for nil values on hash assignment
  # Assuming false is a valid value
  h         = {}
  h[:one]   = one if !one.nil? # local method
  h[:two]   = some_obj.two_method if !some_obj.two_method.nil?
  tmp       = expensive_format_three(some_obj, some_other_obj)
  h[:three] = tmp if !tmp.nil?
  h

  # Delete nil values after hash assignment
  h = {
        :one   => one, # local method
        :two   => some_obj.two_method,
        :three => expensive_format_three(some_obj, some_other_obj)
      }.delete_if { |k, v| v.nil? }