casting ( change type)

to_s:  change to string

ex:

10.to_s

--> “10”

to_i: change to integer

ex:

“10”.to_i

-->  10

ex:

"1a".to_i(16)

---> 26 

to_a: change to array

ex:

(‘1’..’3’).to_a

-->  [“1”, “2”, “3”]