Comments on: named_scope with acts_as_tree

By: benhughes

benhughes — Wed, 29 Jul 2009 11:11:48 +0000

Doing heirarchies more than one sub-level deep cannot be worked with easily since it requires recursive operations to do things like listing *all* children of a given top-level category. In your example above that’s fine and in fact for what you’re doing, since you have to iterate over everything anyways, I’d simply calculate the counts of only the leaf nodes and then calculate in Ruby the counts of parent nodes up from there.

Anyways I can recommend a different approach to heirarchies called the nested set model (http://dev.mysql.com/tech-resources/articles/hierarchical-data.html). With rails there are several plugins implementing this, just search on GitHub for “nested_set”.

By: Camilo Sáchez

Camilo Sáchez — Wed, 29 Jul 2009 03:27:50 +0000

Hi, in my las comment the categories tree are indented for subcategories…

Video Games (15)
——Nintendo DS (3)
———–DS Games (1)
———–DS Lite Consoles (2)
——Nintendo Wii (2)
———–Wii Consoles (1)
———-Wii Games (1)
——PlayStation (10)
———-PS2 Consoles (6)
———-PS3 Accessories (4)

By: Camilo Sáchez

Camilo Sáchez — Wed, 29 Jul 2009 03:24:58 +0000

Hi Ben and thank you so much for this post!

But I have a questions.

How can this?

Video Games (15)
Nintendo DS (3)
DS Games (1)
DS Lite Consoles (2)
Nintendo Wii (2)
Wii Consoles (1)
Wii Games (1)
PlayStation (10)
PS2 Consoles (6)
PS3 Accessories (4)

With you example i have two levels

I need four or five levels – recursive categories

(I need this bad sample)
:conditions => [“categories.id = ? OR categories.parent_id OR categories.grandparent_id = ? OR .. (etc..)

How can count total Products in each parent level?

CategoriesHelper code:

def find_all_listsubcategories(category)
if category.children.size > 0
ret = ”
category.children.each { |subcat|
ret += ”
ret += link_to h(subcat.name), :action => ’show’, :id => subcat
ret += ”
}
ret += ”
end
end

Can you help me please, I’m not a developer. I’m Web designer

Sorry, i don’t speak english very well

thank you again!

By: Javix

Javix — Tue, 10 Feb 2009 09:55:41 +0000

Hi, Ben! I’d like to use acts_as_tree plusgin but I can’t find any examples how to create a new sub-category inside of the given category(i.e. how to pass parent_id to ‘enw-create-edit-update actions).Could you post a simple example, please.Thank you.

By: benhughes

benhughes — Fri, 29 Aug 2008 12:19:26 +0000

You could but that’s an actual find method that returns results, not a scope. My top scope above can be chained. Also, Category.root just returns the *first* result with parent_id = nil (for the case where you have a category with a single root). There is however a Category.roots that works the same way as my top, just not with a named_scope.

By: Martin

Martin — Fri, 29 Aug 2008 10:15:30 +0000

For the first named_scope you could have also used the class method “root” baked into acts_as_tree:

Category.root

By: essetLaf

essetLaf — Sun, 03 Aug 2008 12:04:20 +0000

Thank you

By: mongo

mongo — Wed, 16 Jul 2008 06:34:07 +0000

thank you so much; i was looking for an example with the lambda *and* the association.