Koans question : Don't understand the answers

[roelof]

Hello,

Im trying to learn ruby by using koans.

Now I have to fill in this part.

def test_some_system_objects_always_have_the_same_id
    assert_equal --, false.object_id
    assert_equal --, true.object_id
    assert_equal --, nil.object_id
  end

According to the answers I have to fill in like this :

def test_some_system_objects_always_have_the_same_id
    assert_equal 0, false.object_id
    assert_equal 2, true.object_id
    assert_equal 4, nil.object_id
  end

But how can I normally know the id of a object ?

Roelof

[Robert Walker]

Roelof Wobben wrote in post #1076512:

puts false.object_id
puts true.object_id
puts nil.object_id

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Posted via http://www.ruby-forum.com/.

[Christopher R. Maden]

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On 09/18/2012 01:23 PM, roelof wrote:
> But how can I normally know the id of a object ?

Meditate on the name of the test.

~Chris
- --
Chris Maden, text nerd <URL: http://crism.maden.org/ >
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[rubyonrailsx]

As far as i know, ruby use memory  location to generate object's id, normally any dynamic objects(runtime generate objects) will have different object_id, for example "foo".object_id not equal with "foo".object_id. But, any object like number, true, false ,nil and symbol all have fixed object_id

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rubyonrailsx

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[roelof]

Everybody thanks for the explanation.

I have another problem.
On this :

 def test_accessing_hashes_with_fetch
    hash = { :one => "uno" }
    assert_equal "uno", hash.fetch(:one)
    assert_raise("Class: <IndexError>  Message: <"key not found">  ---Backtrace---  ./about_hashes.rb:27:in `fetch'  ./about_hashes.rb:27:in `test_accessing_hashes_with_fetch' ")  do
      hash.fetch(:doesnt_exist)
    end

I get always a syntax error.

How to solve this one?

Roelof
 

Op woensdag 19 september 2012 05:29:59 UTC+2 schreef cming xu het volgende:

[Frederick Cheung]

On Sep 19, 4:29 am, rubyonrailsx <rubyonrai...@gmail.com> wrote:
> As far as i know, ruby use memory  location to generate object's id, normally any dynamic objects(runtime generate objects) will have different object_id, for example "foo".object_id not equal with "foo".object_id. But, any object like number, true, false ,nil and symbol all have fixed object_id
>

Although this is an implementation detail you'd be I'll advised to
rely on - on my rubinius install for example the object id of nil is
26

Fred

> --
> rubyonrailsx
> Sent with Sparrow (http://www.sparrowmailapp.com/?sig)

>
>
>
>
>
>
>
> On Wednesday, September 19, 2012 at 1:23 AM, roelof wrote:
> > Hello,
>
> > Im trying to learn ruby by using koans.
>
> > Now I have to fill in this part.
>
> > def test_some_system_objects_always_have_the_same_id
> >     assert_equal --, false.object_id
> >     assert_equal --, true.object_id
> >     assert_equal --, nil.object_id
> >   end
>
> > According to the answers I have to fill in like this :
>
> > def test_some_system_objects_always_have_the_same_id
> >     assert_equal 0, false.object_id
> >     assert_equal 2, true.object_id
> >     assert_equal 4, nil.object_id
> >   end
>
> > But how can I normally know the id of a object ?
>
> > Roelof
>
> > --
> > You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group.

> > To post to this group, send email to rubyonra...@googlegroups.com (mailto:rubyonra...@googlegroups.com).
> > To unsubscribe from this group, send email to rubyonrails-ta...@googlegroups.com (mailto:rubyonrails-ta...@googlegroups.com).