When do we use the “||=” operator in Rails ? What is its significance? [duplicate]

Answer 1

This is caching abilities.

a ||= 1  # a assign to 1
a ||= 50 # a is already assigned, a will not be assigned again

puts a
#=> 1

this is useful when u load current user from DB, if this is loaded prior, statement will not try to evaluate right part of equation, which DRY, therefore u can consider it as caching operator.

REF: http://railscasts.com/episodes/1-caching-with-instance-variables