Ruby on Rails, display the name(typ in model) of category

Question

In my projekt i have two models, an "Treatment"-Model and a "Category"-Model

class Category < ActiveRecord::Base
attr_accessible :typ
has_many :treatments
end  

class Treatment < ActiveRecord::Base
belongs_to :patient
belongs_to :category
attr_accessible :content, :day, :typ, :category_typ
end

So in my treatment form the user can also choose the category:

<div class="field">
<%= f.label :category_id %><br />
<%= f.collection_select :category_id, Category.find(:all), :id, :typ %>
</div>

My problem is that later i can display the category_id but i really dont know how i can display the catogory typ:

<% @patient.treatments.each do |treatment| %>
<tr>
<td><%= treatment.category_id %></td>
<td><%= treatment.content %></td>
<td><%= treatment.day %></td>
</tr>
<% end %>

I tried category_typ, but didnt worked! Im beginner in rails and i hope somebody can help me! Thanks!

def show
@patient = Patient.find(params[:id])

respond_to do |format|
  format.html # show.html.erb
  format.json { render json: @patient }
end
end

Try this: treatment.category.try(:typ) If category is not nil, it will display its attribute :typ — MrYoshiji
– MrYoshiji, Commented Jun 16, 2013 at 17:35
Do you know a site where .try is explaind? Somehow i never came in contact with it it? — Em Sta
– Em Sta, Commented Jun 16, 2013 at 17:41
You can find documentation here: apidock.com/rails/Object/try — MrYoshiji
– MrYoshiji, Commented Jun 16, 2013 at 17:45

jvans · Accepted Answer · 2013-06-16 17:51:33Z

1

it works with

  <td><%= treatment.category && treatment.category.typ %></td>

because category is nil for some treatment objects. If treatments need to have a category I would put a validation on the model level as well as a foreign key restrction on the database.

  class Treatment
    validates_presence_of :treatment
  end

and then in a migration

  remove_column :treatments, :category_id
  add_column :treatments, :category_id, :null => false

this will ensure referential integrity in your database. if the relationship is not required then ignore this. You can also make your code 1 method call by using .try

 <td><%= treatment.category.try(:typ)%></td>

answered Jun 16, 2013 at 17:51

jvans

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1 Comment

Em Sta Over a year ago

Because you mentioned validation, i have another question, that refers on validation. Maybe you can help me? stackoverflow.com/questions/17136314/…

Em Sta · Accepted Answer · 2013-06-16 17:39:03Z

1

Ok somehow it works with

<td><%= treatment.category && treatment.category.typ %></td>,

maybe someone knows why this works?

answered Jun 16, 2013 at 17:39

Em Sta

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Comments

Ermin Dedovic · Accepted Answer · 2013-06-16 17:58:37Z

1

You use treatment.category.typ.

You also need @patient = Patient.where(:id => params[:id]).includes(:treatment => [:category]).first in your controller.

edited Jun 16, 2013 at 17:58

answered Jun 16, 2013 at 17:15

Ermin Dedovic

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9 Comments

Em Sta Over a year ago

didnt worked, i get the error undefined method `typ' for nil:NilClass

Ermin Dedovic Over a year ago

You should include category in your query.

Em Sta Over a year ago

how? Sorry im new to rails!

Ermin Dedovic Over a year ago

@EmSta That queries the category and displays the type. But it is performing lazy loading, so if you want better performance, you should go with the query string above.

Ermin Dedovic Over a year ago

No, I mean you should preload your categories like this @patient = Patient.where(:id => params[:id]).includes(:treatment => [:category]).first

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