Ruby still strange to me... ;-)


#1

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… :wink:

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 methoderror_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. :slight_smile:
Josh


#2

On Mar 22, 8:27 pm, Joshua M. removed_email_address@domain.invalid
wrote:

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 methoderror_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


#3

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? :open_mouth:

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:inmethod_missing’
/Users/Josh/Webwork/pgbookings/config/…/app/models/country.rb:10:in
`after_validation’


#4

Hi –

On 3/22/07, Joshua M. removed_email_address@domain.invalid wrote:

{ :not_allowed_chars_in_abbrevation => 'Only characters A-Z are

Now I’m getting such nasty errors againa! Why? :open_mouth:

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:inmethod_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

:slight_smile:

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)


#5

Hi –

On 3/22/07, Joshua M. removed_email_address@domain.invalid wrote:

I’m just wondering… :slight_smile: Already some years ago since I used Java.
I don’t know (I’m not a Java programmer), but someone probably does
:slight_smile: 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)


#6

Thanks a lot for this information. I see, I’m still quite nowhere in
really understanding Ruby, but I’m making progress. :wink:

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… :slight_smile: Already some years ago since I used Java.


#7

On 22-mrt-2007, at 21:27, Joshua M. 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…” ?


#8

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


#9

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


#10

Bart Z. wrote:

On 22-mrt-2007, at 21:27, Joshua M. 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.