This post originated from an RSS feed registered with Ruby Buzz by Florian Frank. Original Post: The opposite of blank? in Rails Feed Title: The Rubylution: Tag Ruby Feed URL: http://rubylution.ping.de/xml/rss/tag/ruby/feed.xml Feed Description: Starts… Now. Latest Ruby Buzz Posts Latest Ruby Buzz Posts by Florian Frank Latest Posts From The Rubylution: Tag Ruby

Ruby on Rails has a core extension that defines blank? for all objects, that are considered to be nil? or empty? and so on. (I think this idea originally came up on the ruby-talk mailing list.)

I often want to use the following code to save a few lines:

if foo = params[:foo]
  # do something with foo
end

Of course this cannot make use of blank? and therefore only works if params[:foo] really is nil. So what am I to do?

It's quite easy to define a Object#full? method like this:

class ::Object
  def full?
    blank? ? nil : self
  end
end

Now it's easy to have the intended semantics:

if foo = params[:foo].full?
  # do something with foo
end

And the code talks equally well to me.

Ok, there is also the situation, where you want to display an associated object in a Rails view, but it can also be nil. It would be nice to be able to pass a block to full? like that:

<%= foo.category.full? { |c| c.name } || '-' %>

This is easy to be added to our full? method:

class ::Object
  def full?
    f = blank? ? nil : self
    if block_given? and f
      yield f
    else
      f
    end
  end
end

This is reasonably short (without much repetition like if and ?:) and much cleaner and less dangerous than to use rescue:

<%= foo.category.name rescue '-' %>