irb(main):001:0> 3.to_i
=> 3

irb(main):002:0> Integer(4)
=> 4

irb(main):003:0> "not_an_int".to_i
=> 0

irb(main):004:0> Integer("not_an_int")
ArgumentError: invalid value for Integer: "not_an_int"
from (irb):4:in `Integer'
                from (irb):4
                from :0
irb(main):005:0>