Question

I have a category model, which is basically what products will be assigned to.

So my category model looks like this:

attr_accessible :name
has_many :category_products do
  def with_products
    includes(:product)
  end
end

has_many :products, :through => :category_products

What I would like to do is to have categories within categories – so a product should be able to be put in Men and then Shoes.

That way, I can have a Men drop-down menu, that produces all the subcategories within Men like Shoes.

But, if a user clicks on Men they will see all the products in that category.

Thoughts?

Answer 1

You can use a gem like Ancestry to organize your categories into a hierarchy.

If you only need one level deep of nesting, you can use a self-join.

belongs_to :parent_category, class: "Category"
has_many :subcategories, class: "Category"

You’ll also need a migration to add category_id to your category table.

Stick a drop down in your app/views/categories/_form.html.erb for category_id and populate it with your list of Categories. You can use this to select a “Parent” for your categories.

Then you can do stuff like:

# Get parent category's name
<%= somecategory.parent.name %>

# Iterate through subcategories
<% someothercategory.subcategories.each do |category| %>
  <%= category.name %>
<% end %>

Using a gem like Ancestry will give you a lot more flexibility when it comes to working with these categories and their associations though.

A bit about how Ancestry works:

Ancestry stores a path from the root to the parent for every node.
This is a variation on the materialised path database pattern. It
allows Ancestry to fetch any relation (siblings, descendants, etc.) in
a single SQL query without the complicated algorithms and
incomprehensibility associated with left and right values.
Additionally, any inserts, deletes and updates only affect nodes
within the affected node’s own subtree.