What does the unary question mark (?) operator do?

Question

I saw this operator in HAML code. I wonder what it is for.

I see the following works:

> ?{
=> \"{\" 
> ?\\s
=> \" \" 
> ?a
=> \"a\"         


        

Answer 1

“?” mark in a ruby method indicates that method will return either true or false.

After checking method name we can determine that this method is going to return boolean value.

Example:

empty? - This method will check whatever the object is empty or not. Depending on that it will return true or false.

Uses:

[1,2,3].empty? - return false

[].empty? - return true