I have a question regarding the ||= statement in ruby and this is of particular interest to me as I'm using it to write to memcache. What I'm wondering is, does ||= check the receiver first to see if it's set before calling that setter, or is it literally an alias to x = x || y

This wouldn't really matter in the case of a normal variable but using something like:

CACHE[:some_key] ||= "Some String"

could possibly do a memcache write which is more expensive than a simple variable set. I couldn't find anything about ||= in the ruby api oddly enough so I haven't been able to answer this myself.

Of course I know that:

CACHE[:some_key] = "Some String" if CACHE[:some_key].nil?

would achieve this, I'm just looking for the most terse syntax.