Question

I’m struggling with the following issue:

$ rails c
Loading development environment (Rails 3.2.1)
irb(main):001:0> 2.class
=> Fixnum
irb(main):002:0> Fixnum === 2
=> true
irb(main):003:0> 2.hours.class
=> Fixnum
irb(main):004:0> Fixnum === 2.hours
=> false
irb(main):005:0> 

I’d like to test whether some specified parameter is a symbol or a time span. The way I thought would be the natural way in Ruby/Rails is:

case param
when :today then
  # do this...
when Fixnum then
  # do that...
else
  raise ArgumentError ...
end

As far as I can tell from ActiveSupport’s source code === is not overridden for Fixnum. So, what am I doing wrong?

Answer 1

You can see from the console, that 2.hours can’t be Fixnum, because it’s #inspect method is overridden. It just pretends to be Fixnum, but it is ActiveSupport::Duration (see the source)

> 2.hours
=> 7200 seconds 
> 2.hours.to_i
=> 7200

Better check if it responds to some methods. If it responds to to_i, it is not a symbol.

> :today.respond_to?(:to_i)
=> false 
> 2.hours.respond_to?(:to_i)
=> true