Date and DateTime on the Mac

Ruby
1

I have installed ruby for Mac OS/X. Strangely, the classes Date and
DateTime
are not known:

NameError: uninitialized constant DateTime
from (irb):1

At least some other classes (I tried File and Time) exist, so it is
not that the
installation were completely broken.

What could be the problem here?

Ronald

2

NameError: uninitialized constant DateTime

Date/DateTime need to be required and aren’t automatically loaded.

require ‘date’
now = DateTime.now

3

On Aug 20, 2007, at 3:50 PM, Ronny wrote:

What could be the problem here?

did you do a

require ‘date’

before trying to access Date or DateTime. They are not part of
the Core classes that are automatically defined when Ruby starts up.

4

On 8/20/07, John J. [email protected] wrote:

It is part of the Ruby ‘standard library’ but you do still need to
require a library before using it.

Is this platform dependent? ‘require’ doesn’t seem to be, er, required
on my SuSE system –

hassan@ceylon:~> ruby -v
ruby 1.8.6 (2007-03-13 patchlevel 0) [x86_64-linux]
hassan@ceylon:~> irb
irb(main):001:0> DateTime.now.to_s
=> “2007-08-20T14:14:31-07:00”
irb(main):002:0>

5

On Aug 20, 2007, at 3:07 PM, Felix W. wrote:

NameError: uninitialized constant DateTime

Date/DateTime need to be required and aren’t automatically loaded.

require ‘date’
now = DateTime.now

It is part of the Ruby ‘standard library’ but you do still need to
require a library before using it.
If you are not sure if a method is available, that is, you don’t know
if it has been required, use irb.
in irb try the method. Error message? then try require ‘library_name’
and it will return true on success, false on failure.
If it returns false, you might have mistyped the name, or path to the
library.

6

On 8/20/07, Gary W. [email protected] wrote:

Be careful with irb. It has its own set of startup rules and
behaviors that are slightly different than Ruby itself. Try:

ruby -e ‘puts DateTime.now.to_s’

Aha, that fails. Good to know – thanks for the clarification.

7

On Aug 20, 2007, at 5:12 PM, Hassan S. wrote:

hassan@ceylon:~> irb
irb(main):001:0> DateTime.now.to_s
=> “2007-08-20T14:14:31-07:00”
irb(main):002:0>

Be careful with irb. It has its own set of startup rules and
behaviors that
are slightly different than Ruby itself. Try:

ruby -e ‘puts DateTime.now.to_s’

Ruby’s startup behaviour can also be changed if the RUBYOPT environment
variable is set.

On my installation irb shows 451 classes defined at startup while the
Ruby
interpreter just shows 147 classes.

8

On Aug 20, 2007, at 4:29 PM, Gary W. wrote:

on my SuSE system –
are slightly different than Ruby itself. Try:

Good call, that’s true, irb does require some things automatically.

9

On Aug 21, 2007, at 4:05 AM, Ronald F. wrote:

cygwin build of Ruby).

Ronald

Ronald F. [email protected]
Phone: +49-89-452133-162

That may mean it’s loading all those libraries on windows even if you
don’t need them…
You might run a test to see if methods from various libraries are
available.

10

did you do a

require ‘date’

before trying to access Date or DateTime. They are not part of
the Core classes that are automatically defined when Ruby starts up.

OK, that solves it - but interestingly, a require ‘date’ is
not necessary when running under Windows (both in the native and
cygwin build of Ruby).

Ronald

11

OK, that solves it - but interestingly, a require ‘date’ is
not necessary when running under Windows (both in the native and
cygwin build of Ruby).
That may mean it’s loading all those libraries on windows
even if you
don’t need them…
You might run a test to see if methods from various libraries are
available.

I wonder whether this is really the “official” definition of Ruby that
date.rb must be required explicitly. On Linux, it isn’t necessary
either,
and at least the Ruby books I have access to (“The Ruby Way” by Hal
Fulton
and “The Ruby Cookbook” by Richardson and Carlson) don’t mention a
require ‘date’ when discussing the Date and DateTime classes…

Ronald