rails/rails — pull request #10673 by sgrif (2013-05-18 00:27:00+00:00)
Title: Add ability to specify how a class is converted to Arel predicate when passed to where

This adds the ability for rails apps or gems to have granular control
over how a domain object is converted to sql. One simple use case would
be to add support for Regexp. Another simple case would be something
like the following:

class DateRange < Struct.new(:start, :end)
def include?(date)
(start..end).cover?(date)
end
end

class DateRangePredicate
def call(attribute, range)
attribute.in(range.start..range.end)
end
end

ActiveRecord::PredicateBuilder.register_handler(DateRange, DateRangePredicate.new)

More complex cases might include taking a currency object and converting
it from EUR to USD before performing the query.

By moving the existing handlers to this format, we were also able to
nicely refactor a rather nasty method in PredicateBuilder.