The Ruby Way: Solutions and Techniques in Ruby Programming, Second Edition

2.24. Converting Strings to Numbers (Decimal and Otherwise)

Basically there are two ways to convert strings to numbers: the Kernel method Integer and Float and the to_i and to_f methods of String. (Capitalized method names such as Integer are usually reserved for special data conversion functions like this.)

The simple case is trivial, and these are equivalent:

x = "123".to_i          # 123
y = Integer("123")      # 123

When a string is not a valid number, however, their behaviors differ:

x = "junk".to_i         # silently returns 0
y = Integer("junk")     # error

to_i stops converting when it reaches a non-numeric character, but Integer raises an error:

x = "123junk".to_i      # 123
y = Integer("123junk")  # error

Both allow leading and trailing whitespace:

x = " 123 ".to_i ...