Where to put this logic: model or controller?

Rails
1

I have an ActiveRecord model called User, here’s my migration and
model:

class CreateUsers < ActiveRecord::Migration
def self.up
create_table :users do |t|
t.column :email, :string, :null => false
t.column :full_name, :string, :null => false
end
end

def self.down
drop_table :users
end
end

class User < ActiveRecord::Base

end

A user has a status. A status is something (a string: “ready”,
“waiting”) that has to be evaluated and cannot be stored to the
database.

My question is about where I should implement the logic (get_status)
to get the user’s status: in the model or the controller? The
controller seems the most logical to me.

I would like to be able to get the status like this, e.g.:

user=User.find(1);
user.status
=> “ready”

So, to implement the above example I would have to have a method
get_status in my user controller? e.g.:

class UsersController < ApplicationController

def show
@user=User.find(1)
@user.get_status

render :json => @user.to_json(:include => @status ) # this should

include the status
end

def get_status
“Ready” # hard coding for now…
end
end

So after the call to show I would get a json string back representing
the User, right?

2

Definitely in the model, business logic should be in the model, the
controller should transform the model for display.

3

To achieve this:

user=User.find(1);
user.status
=> “ready”

You should a method in the model. Then you can access this method
anywhere you have a User object. If you put it in the controller, you
will have to repeat yourself everytime you want User.status

In your model:

def status
“read” if…
etc.
end

In your controller

def show
@user=User.find(1)
#your show view can now read the status method
end

HTH

4

Here’s my user model with the status logic:

class User < ActiveRecord::Base
attr :status, true

def eval_status # this needs to be called anytime User is set
@status=“Ready”
end
end

So now how do I have eval_status called anytime I call User.find…?

5

With status now implimented in the model, when I call:

u=User.find(1)

u.status

=> nil

status isn’t set so it’s null. I need eval_status to be called
somehow.

Any idea?

6

Why don’t you just have the status method return what you need?

class User
def status
“Ready”
end
end

Pat

7

This does the trick:

def evaluate_status
‘Waiting’
end

def status
@status ||= evaluate_status
end

8

On 8/24/07, eggie5 [email protected] wrote:

somehow.

Any idea?

put your initialization code into an after_initialize method, then
it’ll be called both when returning a user via User.new or User.find.

Also, I know you don’t want to store your status or state in the
database, but I just thought I’d mention the acts_as_state_machine
plugin since it may be of some use to you
(http://rails.aizatto.com/category/plugins/acts_as_state_machine/)

Adam

9

Thanks for you help everyone. I remember seeing something like this in
my rails book. It works great now just using the accessor like this:

def status
@status ||= eval_status # eval_status does the work to return
the status
end

I just didn’t know that ruby would automatically call it. So it just
boils down to my ignorance of ruby.

10

On 8/24/07, Brian H. [email protected] wrote:

No… do not use after_initialize if you can avoid it. There are huge
performance penalties, as in… it will be called any time you do a .new, or
each time you create an instance. A finder that gets 50 records will call
this code 50 times, and you can’t turn it off. If you look at the rails
source, you’ll see comments basically warning you not to use
after_initialize and after_find.

thanks for the heads up Brian, I wasn’t aware of the performance
penalty that after_initialize might incur.

Adam

11

No… do not use after_initialize if you can avoid it. There are huge
performance penalties, as in… it will be called any time you do a
.new, or
each time you create an instance. A finder that gets 50 records will
call
this code 50 times, and you can’t turn it off. If you look at the rails
source, you’ll see comments basically warning you not to use
after_initialize and after_find.

The best approach is to override the accessor as eggie5 suggested:

def evaluate_status
‘Waiting’
end

def status
@status ||= evaluate_status
end