help a n00b understand rails, specifically inheritance, acts_as_nested_set, awesome_nested_set, sortable_element_for_nested_set

Question

hey there, i'm trying to implement a drag and drop interface for a nested set in my first rails project. i'm new to rails so bear with me. my code is basically identical to this project: http://gist.github.com/128779. my problem is in the partial at this line:

<% for child in root.direct_children do %>

I'm getting a NoMethodError for direct_children which is an instance method of acts_as_nested_set, I believe. At the console if I try to create a new instance of my model, it is likewise unable to access the acts_as_nested_set instance methods, so I don't think the problem is in the partial but in the model.

Again, sorry if my terminology is wrong, I'm new to rails. Anyway, what am I doing wrong? I've got "acts_as_nested_set" in my model, just like the gist example above but my model does not appear to act as a nested set. How do I go about fixing this?

Thanks!

Here's the code for the model I am using (todo.rb):

class Todo < ActiveRecord::Base
  acts_as_nested_set
end

And here's the partial:

<% content_tag :li, :id => dom_id(root) do %>
    <%= content_tag :span, root.text %>
    <% content_tag :ul do %>
        <% for child in root.direct_children do %>
            <%= render :partial => "tree", :locals => {:root => child}%>
        <%end %>
    <%end unless root.direct_children.empty? %>
<%end%>

root is passed to the partial from the view like:

<%= render :partial => "tree", :locals => {:root => @root} %>

and @root is defined in the controller like:

@root = Todo.find_by_parent_id(nil)

Again, the code is mostly copied wholesale with very few modifications from the gist link above.

What is the `root` you are referring to in the code snippet? — August Lilleaas, Sep 07 '09 at 12:58
Also, we need to see more code, such as the model in question. — August Lilleaas, Sep 07 '09 at 12:58
Hey, thanks! I've added the code above, please let me know if there's anything else needed. — , Sep 07 '09 at 13:45

score 1 · Answer 1 · answered Sep 07 '09 at 21:08

A few things:

Have you checked that you installed the plugin properly? ./script/plugin install git://github.com/rails/acts_as_nested_set.git
Have you set up your table properly? Your model needs to have at least the following 3 columns by default (unless you want to override them): parent_id, lft, rgt. Without these acts_as_nested_set is going to have a hard time figuring out what's going on. I suggest you read the documentation at the top of this file because the readme doesn't say squat, nor does that gist for that matter.
If you've done the above, have you created a root element (not set the parent_id to anything) and then added at least one child to it?
```
m = Model.new
m.title = "My model's title"
m.save!
m2 = Model.new
m2.title = "My child"
m2.save!
m.add_child(m2)
```

I just did a quick test using the above, and afterwards I was able to do things like m.root? and m.direct_children. Good luck.

score 0 · Answer 2 · answered Sep 07 '09 at 18:12

0

What I make from your title is that you're using quite a bit more than acts_as_nested_set. Try removing some plugins and try again.

answered Sep 07 '09 at 18:12

Ariejan

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help a n00b understand rails, specifically inheritance, acts_as_nested_set, awesome_nested_set, sortable_element_for_nested_set

2 Answers2