What does ||= (or-equals) mean in Ruby?

Question

What does the following code mean in Ruby?

||=

Does it have any meaning or reason for the syntax?

Answer 1

a ||= b

Signifies if any value is present in 'a' and you dont want to alter it the keep using that value, else if 'a' doesnt have any value, use value of 'b'.

Simple words, if left hand side if not null, point to existing value, else point to value at right side.