Rails - Jul 2006 - Custom init. of ActiveRecord objects - best practices

All,

I''m wanting to initialize an ActiveRecord object.

I understand that there is a method called after_initialize that appears 
to get called right after the ActiveRecord object is instantiated.

Is after_initialize a Ruby thing or a Rails thing?
Where is after_initialize documented?
Can I pass parameters to it?  If so, how?

I want to initialize the "belongs_to" attribute of my new ActiveRecord
object but can''t figure out how to do it.

Should I just write a standalone public (!) method that will take 
whatever parameters I need to set on my new object and then call this 
method after my call to Object.new? (I''m not calling Object.create so 
before_save is not useful to me here).

In general, what is the best way to perform custom initialization on an 
ActiveRecord object?

Thanks,
Wes

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

Wes Gamble wrote:
> All,
> 
> I''m wanting to initialize an ActiveRecord object.
> 
> I understand that there is a method called after_initialize that appears 
> to get called right after the ActiveRecord object is instantiated.
> 
> Is after_initialize a Ruby thing or a Rails thing?
> Where is after_initialize documented?
> Can I pass parameters to it?  If so, how?
> 
> I want to initialize the "belongs_to" attribute of my new
ActiveRecord
> object but can''t figure out how to do it.
> 
> Should I just write a standalone public (!) method that will take 
> whatever parameters I need to set on my new object and then call this 
> method after my call to Object.new? (I''m not calling Object.create
so
> before_save is not useful to me here).
> 
> In general, what is the best way to perform custom initialization on an 
> ActiveRecord object?
> 
> Thanks,
> Wes

I suppose that if I want to initialize certain fields to default values, 
I have the option of putting login into the appropriate getters to 
handle that, but that seems awfully kludgy.

Wes

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

Based on another post (http://www.ruby-forum.com/topic/13701#4699), I 
think I understand how to handle this.

In order to set the attributes of the job to something custom, you need 
to define

def initialize(attributes)
  super(attributes)
end

where attributes is a hash keyed by attribute name containing the 
default values that you want.

Any further attribute initialization should happen here.

Any initialization of _instance variables_ should probably go into the 
after_initialize method (although it seems like you could include that 
in the
overridden initialize method as well).  there''s no mention of 
after_initialize in the API docs. so I''m not sure if it''s ok
to use or
not.

Here''s my example - I have two models, Job and Contact.  I want to 
initialize Job and set it''s Contact to be the current user.  Note that 
I''m not saving my job yet (so using Job.new, not Job.create).

class Job < ActiveRecord::Base
  belongs_to :contact, :foreign_key => ''ContactNumber''

class Contact < ActiveRecord::Base
  has_many :jobs, :foreign_key => ''ContactNumber''

In my controller, I say:

@current_job = Job.new({ :contact => Contact.find(session[:user]) })

In job.rb, I override the initialize method:

public
def initialize(attributes = nil)
  super(attributes)
  self.FAX = contact.FAX
  self.EMAIL = contact.EMAIL
end

This seems to work.  In my case, I didn''t need to do any initialization
except for attributes so I didn''t define the after_initialize method.

Wes

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