Look for help on Ruby on Rails - ruby

Question

I am new with Ruby on Rails. I just build web application on the existing database. I use rails to generate 2 scaffolds for restaurant and location tables. After that I set relationship for these two tables:
class Restaurant < ActiveRecord::Base
attr_accessible :created, :cuisine_fk, :dish_keywords, :dish_names, :factual_id, :first_name, :last_name, :name, :status
has_many :locations
end
class Location < ActiveRecord::Base
attr_accessible :address1, :address2, :city, :created, :latitude, :longitude, :phone, :restaurant_fk, :state, :status, :url, :zip
belongs_to :restaurant
end
I didn't use "rake db:migrate" after I set up this relationship for these tables, because I was afraid that this action would make changes the existing tables.
When I run this command line
<%= restaurant.location.address1%>
it shows error:
undefined method `location'
" NoMethodError in Restaurants#index
Showing C:/Sites/Dishclips/app/views/restaurants/index.html.erb where line #52 raised:
undefined method `location' for #<Restaurant:0x5853bb8> "
After that I tried to set foreign key for the file:
class Location < ActiveRecord::Base
attr_accessible :address1, :address2, :city, :created, :latitude, :longitude, :phone, :restaurant_fk, :state, :status, :url, :zip
belongs_to :restaurant, :class_name => "Restaurant", :foreign_key => 'restaurant_fk'
end
but it still doen't work.
Is there any way that we can set foreign keys in stead of using "rails db:migrate" after we set up the relationships for tables ? I appreciate your help a lot.

Answer 1

The problem is that you are using location wrongly.
Since the restaurant has_many locations you can't use it the way you mentioned. Because you have an array of locations, actually is a ActiveRecord relationship, so in order to access one of the items assciated you'll have to execute the query and get one of the elements. Here is an example of how to get the first element.
restaurant.locations.first.address1
If the restaurant have only one location, than you should change your model to
class Restaurant < ActiveRecord::Base
attr_accessible :created, :cuisine_fk, :dish_keywords, :dish_names, :factual_id, :first_name, :last_name, :name, :status
has_one :locations
end
and access the property as you are doing:
restaurant.location.address1
Also I'm assuming that your database have the columns you specified, otherwise you'll have to run the migrations.
Regards!

Answer 2

Rails associations are covered very well here in the Rails Guides.
I'll walk you through a basic setup here.
$ rails generate model Restaurant name owner ...
$ rails generate model Location restaurant_id:integer city ...
You then need to migrate your database with rake db:migrate for the database table changes to become effective.
The restaurant_id allows us to set the associations in our models as follows
class Restaurant < ActiveRecord::Base
has_many :locations, dependent: :destroy
attr_accessible :name, :owner
end
class Location < ActiveRecord::Base
belongs_to :restaurant
attr_accessible :city # no restaurant_id here
end
Now you can access your restaurants location as follows.
r = Restaurant.create!(name: '...')
l = Location.create!(city: '...')
# Add association
r.locations << l
r.locations will now return an Array with l in it
l.restaurant will return r
Try to play a little with the different styles of associations, for example by creating new Rails apps quickly and just trying some kind of associations, also some that require a join model.

Answer 3

Now I try this way, then it works. Thank you very much.
<td>
<% restaurant.locations.search(params[:restaurant_fk]).each do |location| %>
<!--address = <%= location.address1 %> + " " + <%= location.address2 %>-->
<%= location.address1 %>
<%= location.address2 %> ,
<%= location.city %> ,
<%= location.state %> ,
<%= location.zip %>
<% end %>
</td>