Date::today not defined?

class, date, ruby

Solution

The `Date` class you are seeing is defined in lib/rubygems/specification.rb for compatibility reasons:

# date.rb can't be loaded for `make install` due to miniruby
# Date is needed for old gems that stored #date as Date instead of Time.
class Date; end

It's an empty class definition and it doesn't provide any methods or functionality.

If starting IRB without RubyGems, that Date class is gone:

$ ruby --disable-gems -S irb
irb(main):001:0> Date
NameError: uninitialized constant Date

Update

The empty `Date` class was removed in RubyGems 2.4.0:

- RubyGems no longer defines an empty Date class. Pull Request #948 by Benoit Daloze.

Problem

Why are only some methods of the Date class loaded without an explicit: ``` require 'date' ``` line? For example: ``` irb(main):002:0> Date.today NoMethodError: undefined method `today' for Date:Class from (irb):2 from /Users/mwlang/.rvm/rubies/ruby-2.0.0-p0/bin/irb:16:in `<main>' ``` And then... ``` irb(main):003:0> require 'date' => true ``` leads to... ``` irb(main):004:0> Date.today => #<Date: 2013-04-12 ((2456395j,0s,0n),+0s,2299161j)> ``` The documentation at http://ruby-doc.org/stdlib-2.0/libdoc/date/rdoc/Date.html seems to offer no explicit explanation for this behavior. Comments on #irc say its a stdlib rather than core library, but core doesn't even have Date class defined and launching irc with -f (suppress reading .irbrc) to get a minimal load still appears to load some sort of base/core Date class. Would like a technical explanation of what's going on and references to the Ruby docs that explain this so I understand for other such encounters as I switch from Ruby 1.8.7 to Ruby 2.0.0.

Original source