Rails - Jan 2010 - ActiveRecord Observers - can it only take one parameter?

hi, guys,

 I refered to http://guides.rubyonrails.org/action_mailer_basics.html
and http://api.rubyonrails.org//

I am a bit unclear about observers.


Consider the set up below:

model/part_mailer.rb
----------------------------
class PartMailer < ActionMailer::Base
  @admin_email =
''admin-p4yIsiyCo27QT0dZR+AlfA@public.gmane.org''
  @from_email =
''admin-sales-p4yIsiyCo27QT0dZR+AlfA@public.gmane.org''

  def created_succesfully(part)
    recipients user.email, @admin_email
    from @from_email
    subject "MyApp - New part created."
    body :user => user
  end

model/part_observer.rb
-------------------------------

class PartObserver < ActiveRecord::Observer
  def after_create(part)
    PartMailer.deliver_created_succesfully(part)
  end
end


It looks as if I can only pass in the object of the given class into
the observer.
In the case above, ''part'' is the only one that is being passed
by to
deliver_created_successfully
in model/part_observer.rb.

 Can I pass more objects to the method, created_successfully (model/
part_mailer.rb)?
I tried looking at the api docs and
http://guides.rubyonrails.org/action_mailer_basics.html
to
no success. Can someone please shed some light into this?

Thanks! :)

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Hi

   You can pass
> class PartMailer < ActionMailer::Base
>   @admin_email =
''admin-p4yIsiyCo27QT0dZR+AlfA@public.gmane.org''
>   @from_email =
''admin-sales-p4yIsiyCo27QT0dZR+AlfA@public.gmane.org''
These are instance variables.If need this entire for the class declare 
it as class varibale using @@
>
And here do like (if this is what you need)

   def created_succesfully(part,pass_what_you_need_here)
>     recipients user.email, @admin_email
>     from @from_email
>     subject "MyApp - New part created."
>     body :user => user
   end
>
Do you mean like this ?
> class PartObserver < ActiveRecord::Observer
   def after_create(part,obj_or_var)
     PartMailer.deliver_created_succesfully(part)
   end
> end
> 
> 



Sijo
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Sijo k g wrote:
> Hi
> 
>    You can pass
>> class PartMailer < ActionMailer::Base
>>   @admin_email =
''admin-p4yIsiyCo27QT0dZR+AlfA@public.gmane.org''
>>   @from_email =
''admin-sales-p4yIsiyCo27QT0dZR+AlfA@public.gmane.org''
> 
> These are instance variables.If need this entire for the class declare 
> it as class varibale using @@
No, actually, that part is fine.  Since the @variables are defined 
outside of a method, they are instance variables on the Class object -- 
they function like @@variables but are apparently more reliable.

Best,
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http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
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hi sijo,
 morning. Thanks for that.

1. Yes I did use class variables in the end.
2. For the parameter arguments to the observer and mailer, yes I did pass in
2 arguments being "user, part" and I got an error being "2 for 1
error" or
that the object, "user" was nil (which is weird because I set up print
statements in the observer to print out various attributes of the
"user"
object (ie. first name, surname and so forth) and it worked fine.

For the time being I stuck to passing 1 parameter argument and used the
object''s associations to grab the other object when I needed it down
the
line. It''s been working well.

Has any body actually done this before ( as in pass in more than 1 parameter
to the observer and the corresponding action method (in my case the
deliver_created_successfully method)?



Thank you :)


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On Thu, Jan 21, 2010 at 1:01 PM, Gordon Yeong
<anexiole-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> hi sijo,
>  morning. Thanks for that.
>
> 1. Yes I did use class variables in the end.
> 2. For the parameter arguments to the observer and mailer, yes I did pass
> in 2 arguments being "user, part" and I got an error being
"2 for 1 error"
> or that the object, "user" was nil (which is weird because I set
up print
> statements in the observer to print out various attributes of the
"user"
> object (ie. first name, surname and so forth) and it worked fine.
>
> For the time being I stuck to passing 1 parameter argument and used the
> object''s associations to grab the other object when I needed it
down the
> line. It''s been working well.
>
> Has any body actually done this before ( as in pass in more than 1
> parameter to the observer and the corresponding action method (in my case
> the deliver_created_successfully method)?
>
>
>
> Thank you :)
>
>
>
Yes, you can use @@some_variable outside of a instance method definition and
access it within an instance method as follows:

@@some_variable

Now, if you use @some_variable outside of a instance method definition, you
can do the following to access it:

@some_variable = some_value_0

class << self
  attribute_accessor :some_variable
end

Then you''ll do the following within an instance method:

PartMailer.some_variable = some_value_1
puts PartMailer.some_variable

In short, top level instance variables loose their scope and must be
qualified using the class name (i.e. <ClassName>.variable_name) within
instance methods instead of using @variable_name.  However, you have direct
access to a top level instance variable within a class method.  For example,
take the following:

class SomeVariable

  @some_variable = 1

  class << self
    attr_accessor :some_variable
  end

  def inner
     print "inner method without qualification => "
     p @some_variable
     print "inner method with qualification => "
     p SomeVariable.some_variable
  end

  def self.outer
    print "outer method => "
    p @some_variable
  end

end

var = SomeVariable.new
var.inner
SomeVariable.outer

Good luck,

-Conrad

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thanks, conrad, makes sense. I will test it out.

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