Testing for existence with “blank?”

I know, I know, all ruby posts should be about slightly new takes on testing paradigms or other amazing best practices, but sometimes I think we skip the basiscs. Today it’s blank?.

ActiveSupport, the Rails extensions to ruby’s standard library introduce the method blank?. It’s pretty handy, and I think people tend to take it for granted without realizing exactly what its semantics are. blank? is handy if you want to treat an empty string, array, or hash as false.

Here’s a slightly haphazard table showing nil?, empty?, and blank? all work.

Input	nil?	empty?	blank?
” “	FALSE	FALSE	TRUE
nil	TRUE	ERROR	TRUE
1	FALSE	ERROR	FALSE
0	FALSE	ERROR	FALSE
“hi”	FALSE	FALSE	FALSE
[]	FALSE	TRUE	TRUE
[ [] ]	FALSE	FALSE	FALSE
[ nil ]	FALSE	FALSE	FALSE
[ 1 ]	FALSE	FALSE	FALSE
true	FALSE	ERROR	FALSE
false	FALSE	ERROR	TRUE
{}	FALSE	TRUE	TRUE
{1=>2}	FALSE	FALSE	FALSE

So if you want a flexible way of testing whether something exists, blank? will often give you what you want. I’m sure that was just thrilling!