# The very model of confusion with models and adding a record to joins

**URL:** <https://www.ruby-forum.com/t/the-very-model-of-confusion-with-models-and-adding-a-record-to-joins/147624>\
**Category:** Rails\
**Created:** [September 3, 2008, 6:13pm UTC](https://www.ruby-forum.com/t/the-very-model-of-confusion-with-models-and-adding-a-record-to-joins/147624 "2008-09-03T18:13:38Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Ruby\_on\_RailsS\_Talk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/dbc845/32.png) [@Ruby\_on\_RailsS\_Talk](https://www.ruby-forum.com/u/Ruby_on_RailsS_Talk)\
**Post date:** [September 3, 2008, 6:13pm UTC](https://www.ruby-forum.com/t/the-very-model-of-confusion-with-models-and-adding-a-record-to-joins/147624/1 "2008-09-03T18:13:38Z")

</div>

Hi (this is an update to a previous problem)

I’ve decided my fundamental problem here is a lack of understanding  
about models. I have enough to get my started by getting lost quickly.

So, following previous advice I have updated my models as such:

class Appointment \< ActiveRecord::Base  
has\_many :line\_items  
belongs\_to :customer  
end

class Customer \< ActiveRecord::Base  
has\_many :line\_items  
has\_many :appointment  
end

class LineItem \< ActiveRecord::Base  
belongs\_to :appointment  
belongs\_to :customer  
belongs\_to :therapist  
has\_many :treatlines  
end

class Therapist \< ActiveRecord::Base  
has\_many :line\_items  
end

class Treatment \< ActiveRecord::Base  
has\_many :treatlines  
end

class Treatline \< ActiveRecord::Base  
belongs\_to :line\_item  
belongs\_to :treatment  
end

I have updated my code which is trying to save lots of information in  
a line\_items (and associated) table using the following code in my  
controller:

def book\_appointment

# Need to write this to take in the date from the date and time

boxes and

# then put it with all the rest of the information to make the

appointment

# Create new appointment

@cart = find\_treat

# Setup data column for the appointment

l = LineItem.new

c = Customer.find(session[:currentcustID])  
t = Therapist.find(params[:appt\_therapist])

# Add a new appointment

a = Appointment.new  
a.appdate = params[:appt\_date]  
a.apptime = params[:appt\_time]  
a.applength = @cart.total\_time  
a.customer = c

l.appointment = a  
l.customer = c  
l.therapist = t

# Need to work out how to add treatments to this massive list!

Refer back to book!  
@cart.items.each do |item|  
if Treatment.find(item.id)  
tr = Treatline.new  
tr.treatment = Treatment.find(item.id)  
logger.warn(“Treatment desclong is:  
#{tr.treatment.desclong}”)  
l.treatlines \<\< tr  
end  
end  
l.save

end

But I’m now getting the following error message:

ActiveRecord::StatementInvalid (Mysql::Error: Column ‘treatline\_id’  
cannot be null: INSERT INTO `line_items` (`updated_at`,  
`therapist_id`, `treatline_id`, `customer_id`, `appointment_id`,  
`created_at`) VALUES(‘2008-09-03 15:00:06’, 2, NULL, 2, 8, ‘2008-09-03  
15:00:06’)):

I felt it would be better for each line item, to keep the treatments  
that each customer has in a seperate table. As each customer can have  
more than one treatment per visist and it’ll make life easier later.  
Hence I’ve now created a table called treatline. This table would, in  
turn, reference the master treatments table which holds all the  
treatments on offer. But I have no idea how to get the line\_items  
table to hold the id for all the treatlines I am associating with an  
order. If that makes sense (and it sure doesn’t seem to be making much  
sense to me at the  
moment!).

It might also help to show you the LineItems model set up as well?

class CreateLineItems \< ActiveRecord::Migration  
def self.up  
create\_table :line\_items do |t|  
t.column :treatline\_id, :integer, :null =\> false  
t.column :customer\_id, :integer, :null =\> false  
t.column :therapist\_id, :integer, :null =\> false  
t.column :appointment\_id, :integer, :null =\> false  
t.timestamps  
end

execute “alter table line\_items add constraint  
fk\_line\_item\_treatlines foreign key (treatline\_id) references  
treatlines(id)”  
execute “alter table line\_items add constraint  
fk\_line\_item\_customers foreign key (customer\_id) references  
customers(id)”  
execute “alter table line\_items add constraint  
fk\_line\_item\_therapists foreign key (therapist\_id) references  
therapists(id)”  
execute “alter table line\_items add constraint  
fk\_line\_item\_appointments foreign key (appointment\_id) references  
appointments(id)”  
execute “alter table treatlines add constraint  
fk\_treatline\_line\_items foreign key (line\_item\_id) references  
line\_items(id)”  
end

def self.down  
drop\_table :line\_items  
end  
end

And treatlines?

class CreateTreatlines \< ActiveRecord::Migration  
def self.up  
create\_table :treatlines do |t|  
t.column :treatment\_id, :integer, :null =\> false  
t.column :line\_item\_id, :integer, :null =\> false  
t.timestamps  
end  
execute “alter table treatlines add constraint  
fk\_treatline\_treatments foreign key (treatment\_id) references  
treatments(id)”

end

def self.down  
drop\_table :treatlines  
end  
end

It’s like being sat with a present. I think I have the right tools to  
get inside the wrapping, but I just can’t seem to get my fingers to  
know they are fingers and not toes. I know my misunderstanding of  
models is at fault here so any help in clearing the fog and getting  
this to save an appointment would be great. I hate only having half  
the knowledge! It’s driving me to drink!

Thanks in advance

Darren

---

<div class="post-metadata">

**Author:** ![Ruby\_on\_RailsS\_Talk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/dbc845/32.png) [@Ruby\_on\_RailsS\_Talk](https://www.ruby-forum.com/u/Ruby_on_RailsS_Talk)\
**Post date:** [September 3, 2008, 8:01pm UTC](https://www.ruby-forum.com/t/the-very-model-of-confusion-with-models-and-adding-a-record-to-joins/147624/2 "2008-09-03T20:01:37Z")

</div>

I feel that you need to clean and simplify your model schema first.

For example i see many unnecessary complications as this:

> class Appointment \< ActiveRecord::Base  
> has\_many :line\_items  
> belongs\_to :customer  
> end
> 
> class Customer \< ActiveRecord::Base  
> has\_many :line\_items  
> has\_many :appointment  
> end

A Customer object can have many Appointment objects associated to it  
and each Appointment can have many LineItems. You can access LineItems  
for a Customer as:

cust.appt.line\_items

I don´t get why you associate directly a Customer to a LineItem. It  
just adds unnecessary complexity.

Next:

> class LineItem \< ActiveRecord::Base  
> belongs\_to :appointment  
> belongs\_to :customer  
> belongs\_to :therapist  
> has\_many :treatlines  
> end

You also "belongs\_to "associate the customer directly. This is  
unnecesary. The customer is linked to LineItems through Appointments.

> class Therapist \< ActiveRecord::Base  
> has\_many :line\_items  
> end

> class Treatment \< ActiveRecord::Base  
> has\_many :treatlines  
> end

> class Treatline \< ActiveRecord::Base  
> belongs\_to :line\_item  
> belongs\_to :treatment  
> end

Here you have a many to many association. Each LineItem can have many  
Treatments and each Treatment can have many LineItems. Treatline is  
just a join model. I could rewrite your complete model as this:

class Customer \< ActiveRecord::Base  
has\_many :appointment  
end

class Appointment \< ActiveRecord::Base  
has\_many :line\_items  
belongs\_to :customer  
end

class LineItem \< ActiveRecord::Base  
belongs\_to :appointment  
belongs\_to :therapist  
has\_many :treatment, :through =\> :treatline  
end

class Therapist \< ActiveRecord::Base  
has\_many :line\_items  
end

class Treatment \< ActiveRecord::Base  
has\_many :line\_items, :through =\> :treatline  
end

class Treatline \< ActiveRecord::Base  
belongs\_to :line\_item  
belongs\_to :treatment  
end

Just add line\_item\_id and treatment\_id to your treatlines table, so  
the associations can be handled correctly, and delete the unnecessary  
\_id columns from your other tables.

And  
voilá!  
You can do this:

cust = Customer.find(\*\*\* customer id _**)  
app = Appointment.create(**_ whatever extra appoinment attributes you  
have \*\*\*)

li = LineItem.create(:therapist\_id =\> therapist\_id, \*\*\* more  
attributes \*\*\*)

or you can do it in two lines, but more readable:

li = LineItem.create(\*\*\* line item atributes)  
li.therapist \<\< Therapist.find(\*\*\* Theraphist ID \*\*\*)

li.treatments \<\< Treatment.find(\*\*\* treatment \_id\*\*\*)  
li.treatments \<\< Treatment.find(\*\*\* another\_treatment\_id \*\*\*)  
app.line\_item \<\< li

cust.appointment \<\< app

You just created a complete appointment for your customer  
This is not tested code, so it may not work at all, but it will give  
you a rough idea of what can be accomplished with proper associations.

Hope it helps.

Regards,  
Jorge Corona.

---

<div class="post-metadata">

**Author:** ![Ruby\_on\_RailsS\_Talk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/dbc845/32.png) [@Ruby\_on\_RailsS\_Talk](https://www.ruby-forum.com/u/Ruby_on_RailsS_Talk)\
**Post date:** [September 3, 2008, 9:29pm UTC](https://www.ruby-forum.com/t/the-very-model-of-confusion-with-models-and-adding-a-record-to-joins/147624/3 "2008-09-03T21:29:00Z")

</div>

I forgot to associate the treatlines table. The models will be like  
this:

class Customer \< ActiveRecord::Base  
has\_many :appointment  
end

class Appointment \< ActiveRecord::Base  
has\_many :line\_items  
belongs\_to :customer  
end

class LineItem \< ActiveRecord::Base  
has\_many :treatline  
belongs\_to :appointment  
belongs\_to :therapist  
has\_many :treatment, :through =\> :treatline  
end

class Therapist \< ActiveRecord::Base  
has\_many :line\_items  
end

class Treatment \< ActiveRecord::Base  
has\_many :treatline  
has\_many :line\_items, :through =\> :treatline  
end

class Treatline \< ActiveRecord::Base  
belongs\_to :line\_item  
belongs\_to :treatment  
end

Regards,  
Jorge Corona.