Question

I have a Model Category which has name:string categoryId:integer parent_id:integer the categoryId doesnt matter in this case I know that it doesnt match the RoR naming convention but I have good reasons for this… Model looks like this:

has_many :children, :class_name => 'Category', :foreign_key => 'parent_id'
belongs_to :parent, :class_name => 'Category', :foreign_key => 'parent_id'
....
...
..
scope :top_categories, where("parent_id IS NULL")

I had a similar problem with the view here and this works well but now i need a dropdown with all the categories displayed in its hierarchie. This is really messing with me i simply dont get it! I want the top categories including the children and the children should include her children,… How can I display this in an array?

I need these data for a collection_select which should display the whole navigation but not on one area I want to display it like this:

Top-Category1
---Sub-Category1
------Sub-Category1-1
------Sub-Category1-2
---Sub-Category2
Top-Category2
---Sub-Category1

Can anyone help me?

// Solved it like this:

  def self.recursive_categories(categories, prefix='')
            c = []
            categories.collect do |cat|
                    current = Struct::Category.new
                    current.id = cat.id
                    current.name =  "#{prefix}#{cat.name}"
                    c << current
                    if cat.children
                           c += recursive_categories( cat.children, prefix + '--' )
                    end
            end
            c
  end

I defined Struct::Category in ApplicationHelper which is included in ApplicationController. Then I used this to display it in form:

<%= f.collection_select :category_id, Category.recursive_categories(Category.top_categories), :id, :name %>

Answer 1

Fairly simple recursion to get the choices array ready for select:

# in a helper
def recursive_options categories, prefix=''
  c = []
  categories.collect do |cat|
    c << [ prefix + cat.name, cat.id ]
    if cat.categories
      c += recursive_options( cat.categories, prefix + '--' )
    end
  end
  c
end

# then in your view somewhere
<%= f.select :category_id, recursive_options( Category.top_categories )