string % 4 -> what is that in ruby

Question

In ruby % is used to format string.

str % arg → new_str

However I do not get

number = '/javascripts/cache/money.js'.bytes.sum % 4

in this commit https://github.com/rails/rails/commit/f6a6b51ae551b7f936e974cba3ad4b30422d6804

Answer 1

It depends on the class of the object.

On a string, % behaves like so:

"Hello, %s" % ['world'] #=> "Hello, world"

Note that in Ruby 1.9.2, you can add names:

"Hello, %{name}" % {:name => "Nick"} #=> "Hello, Nick"

For more details, see the docs.

However, on an integer, it is the modulo function. See the Fixnum docs and the Numeric docs.

Answer 2

I think this % is Integer modulo.

'/javascripts/cache/money.js'.bytes  returns an Enumerator

'/javascripts/cache/money.js'.bytes.sum   returns an Integer

'/javascripts/cache/money.js'.bytes.sum % 4   returns an Integer

They may have defined the sum method themselves, which may be the reason for the question?