Rails - Dec 2006 - newbie question, "show items in selected city and category"

Hi,
rails newbie needs help :)

I have classified ads (cads) related with cities and categories:


class Cad < ActiveRecord::Base
     has_and_belongs_to_many :categories
     has_and_belongs_to_many :cities
 end

class Category < ActiveRecord::Base
    has_and_belongs_to_many :cads
end

class City < ActiveRecord::Base
    has_and_belongs_to_many :cads
end

I assume that user can act such way: first, from cities listing, which
is produced by ''list'' method in cities_controller, the user
chooses
city ( clicks on ''show'' link).

cities_controller#show contains the following:
def show
    @city = City.find(params[:id])
    @cads = @city.cads
    @categories_of_cads_in_city = @cads.map {|cad|
cad.categories}.flatten.uniq
end

So,  the user sees classified ads and categories of these ads:

cities/show.rhtml:
[...]
<% @cads.each do |cad| %>
<%=link_to cad.title,
		:controller => "cads",
		:action => "show",
		:id => cad.id
%>

<% @categories_of_cads_in_city.each do |category| %>
<%= link_to category.name,
		:controller => "categories",
		:action => "show",
		:id => category.id
%>
[...]

The next thing user may want to do - see classified ads in some
category of chosen city (assume in "Health" category) , so he clicks
on
link "Health".
So i must find ads which are associated with chosen city and category
"Health". How can i do achieve this ?? 
Thanks


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ogurec wrote:
> class Cad < ActiveRecord::Base
>      has_and_belongs_to_many :categories
>      has_and_belongs_to_many :cities
>  end
>
> class Category < ActiveRecord::Base
>     has_and_belongs_to_many :cads
> end
>
> class City < ActiveRecord::Base
>     has_and_belongs_to_many :cads
> end
>
> So i must find ads which are associated with chosen city and category
> "Health". How can i do achieve this ??
This is untested, and there may be an easier way, but this should work:

class Cad
  def self.with_category_and_city(category, city)
    with_scope :find => {:conditions => ["categories.id = ? AND
cities.id = ?", category.id, city.id], :include => [:categories,
:cities]} do
      yield
    end
  end

  def self.find_by_category_and_city(category, city, *args)
    with_category_and_city(category, city) { find(*args) }
  end
end

Set up like this, the Cad.find_by_category_and_city method will take
standard ActiveRecord::Base.find options.

Example:
  Cad.find_by_category_and_city(@category, @city, :first)
  Cad.find_by_category_and_city(@category, @city, :all, :order =>
"cads.name")

Dan Manges


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Many thanks Dan,
i''ve added method ''category'' into
''cities_controller'' and its works!

I understand how @category gets its value regarding passed id, but how
can i get the value of @city that was previously set in
cities_controller#show ?

cities_controller#category
@city = City.find(1)
@category = Category.find(params[:id])
@cads = Cad.find_by_category_and_city(@category, @city, :all)


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ogurec wrote:
> Many thanks Dan,
> i''ve added method ''category'' into
''cities_controller'' and its works!
>
> I understand how @category gets its value regarding passed id, but how
> can i get the value of @city that was previously set in
> cities_controller#show ?
>
> cities_controller#category
> @city = City.find(1)
> @category = Category.find(params[:id])
> @cads = Cad.find_by_category_and_city(@category, @city, :all)
I would pass both the ID for the city and the ID for category to your
''category'' action.

Example, in the /cities/show view:
<% for category in @categories %>
  <%= link_to h(category.name), :action => ''category'',
:id => @city,
:category => category %>
<% end %>

The with the default routes the URL will be like:
/cities/category/1?category=3
And then in the controller for that action:
@city = City.find(params[:id])
@category = Category.find(params[:category])

Dan Manges


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Thanks a lot!


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