From: Robert Klemme <shortcutter@...>
Date: 2007-11-29T19:35:06+09:00
Subject: Re: hash.clear("value")

2007/11/28, MonkeeSage <MonkeeSage@gmail.com>:
> On Nov 28, 1:47 pm, Andrew Stone <stoneli...@gmail.com> wrote:
> > Note:  parts of this message were removed by the gateway to make it a legal Usenet post.
> >
> > Hello all,
> >
> > Was just wondering if there was something simple like:
> >
> > hash.clear("value")
> >
> > This would remove all entries from the hash whose value == "value".
> >
> > Yeah, I know about delete_if, this would just be more succinct.  I can be
> > lazy sometimes.
> >
> > thanks,
> > andy
> >
> > --
> > Andrew Stone
>
> You can always wrap delete_if...
>
> class Hash
>   def remove(target)
>     self.delete_if { | key, value |
>       value == target
>     }
>   end
> end

Just a subtle point: IMHO it is better to put "target" on the left
side of the comparison because that gives the caller more control on
the deletion criterion:

class Hash
 def remove(target)
   delete_if { | key, value |
     target == value
   }
 end
end

For example, you could do

crit = Object.new
def crit.==(x) x < 10 end
a_hash.remove crit # remove all entries where value is < 10

It's a similar pattern to how "case" does comparison via "===".  But
then again, this is probably even better:

class Hash
  def remove_val
    delete_if {|k,v| yield v}
    self
  end
end

Because it's more modular.  But then again, you can use delete_if directly. :-)

Kind regards

robert


-- 
use.inject do |as, often| as.you_can - without end