It is a common misunderstanding that all [op]=-operators work the same way, but actually they don't.
||= and &&=
Those are special cases, because the assignment will only happen if the first variable passes the check (false or nil for || and true for &&).
a ||= b # => a || (a = b)
a &&= b # => a && (a = b)
But still, if reading a has any side effects, they will take place regardless of to what a resolves.
Other [op]=
Assignment will always take place, no matter the value of a.
a += b # => a = a + b
a -= b # => a = a - b
ary1 |= ary2 # => ary1 = ary1 | ary2
#...
For example array union:
ary1 = ['a', 'b', 'c']
ary2 = ['c', 'd', 'a']
ary1 |= ary2
# => ['a', 'b', 'c', 'd']
Posted to makandra dev (2015-04-23 09:00)