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eggie5

2007-Aug-23 23:15 UTC

Calling a method on class creation

I have a model User that has property called status. Status is just a
string that can only be evaluated and not persisted. I.e. it doesn''t
have a field in the user table.

Anyways, I would like a method get_status to be called anytime I
create a new instance of User. For example:

user=User.new

Since I created a new instance of User, I should now have access to
the status property, e.g.:

user.status
=>"Ready"

Here is my User class:

class User < ActiveRecord::Base
  has_and_belongs_to_many :roles

def evaluate_status
    #evaluate the status
    #@status = ...
  end
end

How would I call get_status whenever a new instance of User is
created? It''s constructor?

Thanks


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dang

2007-Aug-24 00:18 UTC

head link

Re: Calling a method on class creation

initialize or after_initialize should do what you need. Initialize is
called by ruby when the object is, well, initialized...

cheers,
Dan

================================class User < ActiveRecord::Base
  has_and_belongs_to_many :roles

  def initialize
    evaluate_status
  end

  def evaluate_status
    #evaluate the status
    #@status = ...
  end
end
================================


On Aug 24, 9:15 am, eggie5
<egg...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> I have a model User that has property called status. Status is just a
> string that can only be evaluated and not persisted. I.e. it
doesn''t
> have a field in the user table.
>
> Anyways, I would like a method get_status to be called anytime I
> create a new instance of User. For example:
>
> user=User.new
>
> Since I created a new instance of User, I should now have access to
> the status property, e.g.:
>
> user.status
> =>"Ready"
>
> Here is my User class:
>
> class User < ActiveRecord::Base
>   has_and_belongs_to_many :roles
>
> def evaluate_status
>     #evaluate the status
>     #@status = ...
>   end
> end
>
> How would I call get_status whenever a new instance of User is
> created? It''s constructor?
>
> Thanks

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eggie5

2007-Aug-24 05:11 UTC

head link

Re: Calling a method on class creation

It doesn''t seem like the initializer gets called when you create a new
instance using .find(), e.g.:

c=ContentCampaign.find(1)
c.status

=> nill

However, If I create a new instance using new it works, e.g:

d=ContentCampaign.new
c.status
=> Waiting

Here is my class, what''s going on?

class ContentCampaign < ActiveRecord::Base
  belongs_to :category, :class_name => "Category", :foreign_key
=>
"category_id"

  def initialize
   @status= evaluate_status
  end


  def evaluate_status
    ''Waiting''
  end

  def status
    @status
  end

end


On Aug 23, 5:18 pm, dang <dgr...-vQs5aMGR+7nQT0dZR+AlfA@public.gmane.org>
wrote:> initialize or after_initialize should do what you need. Initialize is
> called by ruby when the object is, well, initialized...
>
> cheers,
> Dan
>
> ================================> class User < ActiveRecord::Base
>   has_and_belongs_to_many :roles
>
>   def initialize
>     evaluate_status
>   end
>
>   def evaluate_status
>     #evaluate the status
>     #@status = ...
>   end
> end
> ================================>
> On Aug 24, 9:15 am, eggie5
<egg...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > I have a model User that has property called status. Status is just a
> > string that can only be evaluated and not persisted. I.e. it
doesn''t
> > have a field in the user table.
>
> > Anyways, I would like a method get_status to be called anytime I
> > create a new instance of User. For example:
>
> > user=User.new
>
> > Since I created a new instance of User, I should now have access to
> > the status property, e.g.:
>
> > user.status
> > =>"Ready"
>
> > Here is my User class:
>
> > class User < ActiveRecord::Base
> >   has_and_belongs_to_many :roles
>
> > def evaluate_status
> >     #evaluate the status
> >     #@status = ...
> >   end
> > end
>
> > How would I call get_status whenever a new instance of User is
> > created? It''s constructor?
>
> > Thanks

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Sava Chankov

2007-Aug-24 12:37 UTC

head link

Re: Calling a method on class creation

eggie5 wrote:> It doesn''t seem like the initializer gets called when you create a
new
> instance using .find(), e.g.:
> 
> c=ContentCampaign.find(1)
> c.status
> 
> => nill
> 
> However, If I create a new instance using new it works, e.g:
> 
> d=ContentCampaign.new
> c.status
> => Waiting
> 
> Here is my class, what''s going on?
> 
> class ContentCampaign < ActiveRecord::Base
>   belongs_to :category, :class_name => "Category",
:foreign_key =>
> "category_id"
> 
>   def initialize
>    @status= evaluate_status
>   end
> 
> 
>   def evaluate_status
>     ''Waiting''
>   end
> 
>   def status
>     @status
>   end
> 
> end
Try instead:

class ContentCampaign < ActiveRecord::Base
  belongs_to :category, :class_name => "Category", :foreign_key
=>"category_id"


  def evaluate_status
    ''Waiting''
  end

  def status
    @status ||= evaluate_status
  end
end


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eggie5

2007-Aug-24 19:04 UTC

head link

Re: Calling a method on class creation

THANKS! that''s the trick I was looking for. Now this reminds me of an
example from the essential rails book...

So, it looks like status is called automatically when a new instance
of the class is created?

On Aug 24, 5:37 am, Sava Chankov
<sava.chan...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> eggie5 wrote:
> > It doesn''t seem like the initializer gets called when you
create a new
> > instance using .find(), e.g.:
>
> > c=ContentCampaign.find(1)
> > c.status
>
> > => nill
>
> > However, If I create a new instance using new it works, e.g:
>
> > d=ContentCampaign.new
> > c.status
> > => Waiting
>
> > Here is my class, what''s going on?
>
> > class ContentCampaign < ActiveRecord::Base
> >   belongs_to :category, :class_name => "Category",
:foreign_key =>
> > "category_id"
>
> >   def initialize
> >    @status= evaluate_status
> >   end
>
> >   def evaluate_status
> >     ''Waiting''
> >   end
>
> >   def status
> >     @status
> >   end
>
> > end
>
> Try instead:
>
> class ContentCampaign < ActiveRecord::Base
>   belongs_to :category, :class_name => "Category",
:foreign_key
> =>"category_id"
>
>   def evaluate_status
>     ''Waiting''
>   end
>
>   def status
>     @status ||= evaluate_status
>   end
> end

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Adam Cohen

2007-Aug-24 19:09 UTC

head link

Re: Calling a method on class creation

On 8/24/07, eggie5 <eggie5-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:>
> THANKS! that''s the trick I was looking for. Now this reminds me of
an
> example from the essential rails book...
>
> So, it looks like status is called automatically when a new instance
> of the class is created?
does defining an after_initialize method not work for you?

by the way, your belongs_to method doesn''t need the :class_name or
:foreign_key specifications.. These can be inferred from the
association itself.

Adam

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eggie5

2007-Aug-24 19:58 UTC

head link

Re: Calling a method on class creation

sorry I didn''t see you solution till after I tried accessor method.

Regarding the foreign_key and class_name things, rails was warning me
that if I could, I should specify them to avoid confusion. Since it
was not big deal I just put them in. It''s the least I could do for
ActiveRecord!

On Aug 24, 12:09 pm, "Adam Cohen"
<bionicboo...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> On 8/24/07, eggie5 <egg...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
>
>
> > THANKS! that''s the trick I was looking for. Now this reminds
me of an
> > example from the essential rails book...
>
> > So, it looks like status is called automatically when a new instance
> > of the class is created?
>
> does defining an after_initialize method not work for you?
>
> by the way, your belongs_to method doesn''t need the :class_name or
> :foreign_key specifications.. These can be inferred from the
> association itself.
>
> Adam

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