.nil? can be used on any object and is true if the object is nil.
.empty? can be used on strings, arrays and hashes and returns true if:
- String length == 0
- Array length == 0
- Hash length == 0
Running .empty? on something that is nil will throw a NoMethodError.
That is where .blank? comes in. It is implemented by Rails and will operate on any object as well as work like .empty? on strings, arrays and hashes.
nil.blank? == true
false.blank? == true
[].blank? == true
{}.blank? == true
"".blank? == true
5.blank? == false
0.blank? == false
.blank? also evaluates true on strings which are non-empty but contain only whitespace:
" ".blank? == true
" ".empty? == false
Rails also provides .present?, which returns the negation of .blank?.
Array gotcha: blank? will return false even if all elements of an array are blank. To determine blankness in this case, use all? with blank?, for example:
[ nil, '' ].blank? == false
[ nil, '' ].all? &:blank? == true
The statement goes through the conditions in order, will stop when a falsy result is obtained and return the value of the last evaluation performed.
In contrary to && which stops at a falsy value, || will stop at a truthy value instead.
Best Answer
In Ruby, everything is an expression, and an expression will return the last value evaluated within it.
For both of your examples, the left side of the
||expression evaluates to a falsy value, so Ruby then evaluates the right side, and returns it.