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Joshua Muheim

2007-Mar-22 20:27 UTC

Ruby still strange to me... ;-)

Hi all

Always when I begin to think that I''m getting better and better in
mastering Ruby I stumble upon some strange behavior that I don''t
understand... ;-)

class Country < ActiveRecord::Base
  validates_presence_of :abbrevation
  validates_presence_of :name
  validates_format_of :abbrevation,
    :with => /[a-z]{2}/i,
    :message => self.error_messages[:not_allowed_chars_in_abbrevation]

  def self.error_messages
    { :not_allowed_chars_in_abbrevation => ''Only characters A-Z are
allowed''}
  end
end

This gives me the following error:

usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/base.rb:1235:in
`method_missing'': undefined local variable or method
`error_messages''
for Country:Class (NameError)
        from
/Users/Josh/Webwork/pgbookings/config/../app/models/country.rb:6
        ...

And I don''t have a clue what''s wrong here... :-/ Thanks for a
hint. :-)
Josh

-- 
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Chris Mear

2007-Mar-22 20:36 UTC

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Re: Ruby still strange to me... ;-)

On Mar 22, 8:27 pm, Joshua Muheim
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:> class Country < ActiveRecord::Base
>   validates_format_of :abbrevation,
>     :with => /[a-z]{2}/i,
>     :message => self.error_messages[:not_allowed_chars_in_abbrevation]
>
>   def self.error_messages
>     { :not_allowed_chars_in_abbrevation => ''Only characters A-Z
are
> allowed''}
>   end
> end
>
> This gives me the following error:
>
> usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/base.rb:12
35:in
> `method_missing'': undefined local variable or method
`error_messages''
> for Country:Class (NameError)
>         from
> /Users/Josh/Webwork/pgbookings/config/../app/models/country.rb:6
Try putting the definition of error_messages above the place where you
use it.

Chris


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Joshua Muheim

2007-Mar-22 20:50 UTC

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Re: Ruby still strange to me... ;-)

Thanks, this drove me into the right direction.

Anyway, I changed my design a little bit:

class Country < ActiveRecord::Base
  validates_presence_of :abbrevation
  validates_presence_of :name

  def self.error_messages
    { :not_allowed_chars_in_abbrevation => ''Only characters A-Z are 
allowed''}
  end

  def after_validation
    @errors.add(:abbrevation, 
self.error_messages[:not_allowed_chars_in_abbrevation]) if 
!@errors.on(:abbrevation) and @abbrevation !~ /^[a-z]{2}$/i
  end
end

Now I''m getting such nasty errors againa! Why? :O

NoMethodError: undefined method `error_messages'' for 
#<Country:0x25b3c58>
   
/usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/base.rb:1860:in
`method_missing''
    /Users/Josh/Webwork/pgbookings/config/../app/models/country.rb:10:in 
`after_validation''
    ...

-- 
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David A. Black

2007-Mar-22 21:34 UTC

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Re: Ruby still strange to me... ;-)

Hi --

On 3/22/07, Joshua Muheim
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:>
> Thanks, this drove me into the right direction.
>
> Anyway, I changed my design a little bit:
>
> class Country < ActiveRecord::Base
>   validates_presence_of :abbrevation
>   validates_presence_of :name
>
>   def self.error_messages
>     { :not_allowed_chars_in_abbrevation => ''Only characters A-Z
are
> allowed''}
>   end
>
>   def after_validation
>     @errors.add(:abbrevation,
> self.error_messages[:not_allowed_chars_in_abbrevation]) if
> !@errors.on(:abbrevation) and @abbrevation !~ /^[a-z]{2}$/i
>   end
> end
>
> Now I''m getting such nasty errors againa! Why? :O
>
> NoMethodError: undefined method `error_messages'' for
> #<Country:0x25b3c58>
>    
/usr/lib/ruby/gems/1.8/gems/activerecord-1.15.3/lib/active_record/base.rb:1860:in
> `method_missing''
>     /Users/Josh/Webwork/pgbookings/config/../app/models/country.rb:10:in
> `after_validation''
Like most questions about Ruby, it comes down to:

  1. an object can have its own methods
  2. classes are objects too

:-)

You''ve defined error_messages as a singleton method for your class (a
class method), but then you''re trying to call it on a totally
different object, namely an *instance* of your class.


David

-- 
Q. What is THE Ruby book for Rails developers?
A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
   (See what readers are saying!  http://www.rubypal.com/r4rrevs.pdf)
Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
A. Ruby Power and Light, LLC (http://www.rubypal.com)

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Joshua Muheim

2007-Mar-22 21:45 UTC

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Re: Ruby still strange to me... ;-)

Thanks a lot for this information. I see, I''m still quite nowhere in 
really understanding Ruby, but I''m making progress. ;-)

Is it possible that in Java on can call class methods (static methods) 
from the class itself and from an instantiated object?

MyClass.staticMethod() => someValue
myClassObj.staticMethod() => someValue

I''m just wondering... :-) Already some years ago since I used Java.

-- 
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David A. Black

2007-Mar-22 22:48 UTC

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Re: Ruby still strange to me... ;-)

Hi --

On 3/22/07, Joshua Muheim
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:>
> Thanks a lot for this information. I see, I''m still quite nowhere
in
> really understanding Ruby, but I''m making progress. ;-)
>
> Is it possible that in Java on can call class methods (static methods)
> from the class itself and from an instantiated object?
>
> MyClass.staticMethod() => someValue
> myClassObj.staticMethod() => someValue
>
> I''m just wondering... :-) Already some years ago since I used
Java.
I don''t know (I''m not a Java programmer), but someone probably
does
:-)  In Ruby, you can do:

  class MyClass
     def self.some_class_method
        # ...
     end

     def an_instance_method
        self.class.some_class_method
     end
  end

Basically, as long as you can get hold of an object that understands
what you''re asking it to do (in this case, the object in question is
self.class), you can ask it to do it.


David

-- 
Q. What is THE Ruby book for Rails developers?
A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
   (See what readers are saying!  http://www.rubypal.com/r4rrevs.pdf)
Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
A. Ruby Power and Light, LLC (http://www.rubypal.com)

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Michael Kovacs

2007-Mar-22 22:55 UTC

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Re: Ruby still strange to me... ;-)

Yes java and ruby work the same in this manner. You can call static  
or class level methods from either another static or an instance

-Michael
http://javathehutt.blogspot.com

On Mar 22, 2007, at 3:48 PM, David A. Black wrote:
>
> Hi --
>
> On 3/22/07, Joshua Muheim
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:
>>
>> Thanks a lot for this information. I see, I''m still quite
nowhere in
>> really understanding Ruby, but I''m making progress. ;-)
>>
>> Is it possible that in Java on can call class methods (static  
>> methods)
>> from the class itself and from an instantiated object?
>>
>> MyClass.staticMethod() => someValue
>> myClassObj.staticMethod() => someValue
>>
>> I''m just wondering... :-) Already some years ago since I used
Java.
>
> I don''t know (I''m not a Java programmer), but someone
probably does
> :-)  In Ruby, you can do:
>
>   class MyClass
>      def self.some_class_method
>         # ...
>      end
>
>      def an_instance_method
>         self.class.some_class_method
>      end
>   end
>
> Basically, as long as you can get hold of an object that understands
> what you''re asking it to do (in this case, the object in question
is
> self.class), you can ask it to do it.
>
>
> David
>
> -- 
> Q. What is THE Ruby book for Rails developers?
> A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
>    (See what readers are saying!  http://www.rubypal.com/r4rrevs.pdf)
> Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
> A. Ruby Power and Light, LLC (http://www.rubypal.com)
>
> >

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Bart Zonneveld

2007-Mar-23 02:45 UTC

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Re: Ruby still strange to me... ;-)

On 22-mrt-2007, at 21:27, Joshua Muheim wrote:
>
> Hi all
>
> Always when I begin to think that I''m getting better and better in
> mastering Ruby I stumble upon some strange behavior that I don''t
> understand... ;-)
>
> class Country < ActiveRecord::Base
>   validates_presence_of :abbrevation
>   validates_presence_of :name
>   validates_format_of :abbrevation,
>     :with => /[a-z]{2}/i,
>     :message => self.error_messages[:not_allowed_chars_in_abbrevation]
>
>   def self.error_messages
>     { :not_allowed_chars_in_abbrevation => ''Only characters A-Z
are
> allowed''}
>   end
> end
Not too sure about the R(oR) error, but why don''t you use :message
=>
"Only etc.." ?


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Ben Munat

2007-Mar-23 06:16 UTC

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Re: Ruby still strange to me... ;-)

Well I wouldn''t say that they work exactly the same... You
can''t call a
class method on an instance directly (foo.some_class_method), but you 
can call it on the class of the instance (foo.class.some_class_method).

In java, you can call the static method on the instance but it''s a 
compiler warning ("Static method should be accessed in a static
way")...
you''re supposed to call static methods on the class itself.

b

Michael Kovacs wrote:> Yes java and ruby work the same in this manner. You can call static  
> or class level methods from either another static or an instance
> 
> -Michael
> http://javathehutt.blogspot.com
> 
> On Mar 22, 2007, at 3:48 PM, David A. Black wrote:
> 
>> Hi --
>>
>> On 3/22/07, Joshua Muheim
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:
>>> Thanks a lot for this information. I see, I''m still quite
nowhere in
>>> really understanding Ruby, but I''m making progress. ;-)
>>>
>>> Is it possible that in Java on can call class methods (static  
>>> methods)
>>> from the class itself and from an instantiated object?
>>>
>>> MyClass.staticMethod() => someValue
>>> myClassObj.staticMethod() => someValue
>>>
>>> I''m just wondering... :-) Already some years ago since I
used Java.
>> I don''t know (I''m not a Java programmer), but someone
probably does
>> :-)  In Ruby, you can do:
>>
>>   class MyClass
>>      def self.some_class_method
>>         # ...
>>      end
>>
>>      def an_instance_method
>>         self.class.some_class_method
>>      end
>>   end
>>
>> Basically, as long as you can get hold of an object that understands
>> what you''re asking it to do (in this case, the object in
question is
>> self.class), you can ask it to do it.
>>
>>
>> David
>>
>> -- 
>> Q. What is THE Ruby book for Rails developers?
>> A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
>>    (See what readers are saying!  http://www.rubypal.com/r4rrevs.pdf)
>> Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
>> A. Ruby Power and Light, LLC (http://www.rubypal.com)
>>
> 
> 
> > 
> 
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Joshua Muheim

2007-Mar-23 07:21 UTC

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Re: Ruby still strange to me... ;-)

Bart Zonneveld wrote:> On 22-mrt-2007, at 21:27, Joshua Muheim wrote:
> 
>>   validates_format_of :abbrevation,
>>     :with => /[a-z]{2}/i,
>>     :message =>
self.error_messages[:not_allowed_chars_in_abbrevation]
>>
>>   def self.error_messages
>>     { :not_allowed_chars_in_abbrevation => ''Only characters
A-Z are
>> allowed''}
>>   end
>> end
> 
> Not too sure about the R(oR) error, but why don''t you use :message
=>
> "Only etc.." ?
Because I''m using Unit tests with something like that:

assert_equal(@country.errors.on(:abbrevation), 
Country.error_messages[:not_allowed_chars_in_abbrevation])

That way I can e.g. i18n the project without having hard programmed unit 
tests.

-- 
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Rails - Mar 2007 - Ruby still strange to me... ;-)

Ruby still strange to me... ;-)

Re: Ruby still strange to me... ;-)

Re: Ruby still strange to me... ;-)

Re: Ruby still strange to me... ;-)

Re: Ruby still strange to me... ;-)

Re: Ruby still strange to me... ;-)

Re: Ruby still strange to me... ;-)

Re: Ruby still strange to me... ;-)

Re: Ruby still strange to me... ;-)

Re: Ruby still strange to me... ;-)