Rails - Feb 2006 - how to better generalize a tree?

first some background info:
I have a blog application that has a comments table with the following columns:
id
parent_id
post_id
created_at
body

here''s my model:

class Comment < ActiveRecord::Base
  belongs_to :post
  acts_as_tree :order => ''created_at''

  def print_children (options={})
    before          = options[:before]          ? options[:before]          :
''''
    after           = options[:after]           ? options[:after]           :
''''
    before_children = options[:before_children] ? options[:before_children] :
''''
    after_children  = options[:after_children]  ? options[:after_children]  :
''''

    output = ''''

    for child in children
      output += before
      output += child.body
      if !child.children.empty?
        output += before_children
        output += child.print_children options
        output += after_children
      end
      output += after
    end
    return output
  end
end

the print_children method takes several options, for example, in my
view it call it like:

<ul>
<% for comment in @comments %>
    <li>
        <%= comment.body %>
        <% if !comment.children.empty? %>
        <ul>
          <%= comment.print_children :before =>
''<li>'',
                                     :after =>
''</li>'',
                                     :before_children =>
''<ul>'',
                                     :after_children =>
''</ul>'' %>
        </ul>
        <% end %>
    </li>
<% end %>
</ul>

@comments is an array of all the comments for the current post where
parent_id is null (each of those potentially has a tree of comments
beneath it)
that will give me all the comments in nice nested lists.

Now for the question. Is there a way to make something like this use a
partial template, such that, for each comment, I could render a
template, instead of passing several options to print_children? The
way it works now, if i want to display more comment properties (for
example, created_at, or in the future, the author) or if i wanted to
format each comment in some odd way I have to change both my template
AND my print_children method.


-Dana

The solution is to use a recursive partial template, this keeps all the
display code in view where it belongs.

the model:
class Comment < ActiveRecord::Base
  belongs_to :post
  acts_as_tree :order => ''created_at''
end

the main template:

<div class="comments">
<ul>
  <% for comment in @comments %>
    <%= render :partial => ''comment'', :locals =>
{:comment => comment}
%>
  <% end %>
</ul>
</div>

and the partial template (_comment.rhtml), notice how it renders itself:

<li>
  <div>
    <%= comment.body %>
  </div>
  <% if !comment.children.empty? %>
    <ul>
      <% for comment in comment.children %>
        <%= render :partial => ''comment'', :locals =>
{:comment =>
comment } %>
      <% end %>
    </ul>
  <% end %>
</li>

-- 
Posted via http://www.ruby-forum.com/.

Dana wrote:
I can''t believe I wrote the same kind of code today. I chose to use the
:collection member of the options hash to let Rails iterate the 
collections. This just happens to be my application -- a menu tree -- 
but it looks pretty much like any other kind of tree:)

BTW: This can be also accomplished very nicely with Builder::XmlMarkup 
used in a simple recursion.

template:

<ul>
  <%= render :partial => ''menu_list'', :collection =>
@menus %>
</ul>

partial:

<li>
  <%= menu_list.menu_name %>
  <% if menu_list.has_children? -%>
  <ul>
    <%= render(:partial => ''menu_list'', :collection
=>
menu_list.children)  %>
  </ul>
<% end -%>
</li>

> the main template:
> 
> <div class="comments">
> <ul>
>   <% for comment in @comments %>
>     <%= render :partial => ''comment'', :locals =>
{:comment => comment}
> %>
>   <% end %>
> </ul>
> </div>
> 
> and the partial template (_comment.rhtml), notice how it renders itself:
> 
> <li>
>   <div>
>     <%= comment.body %>
>   </div>
>   <% if !comment.children.empty? %>
>     <ul>
>       <% for comment in comment.children %>
>         <%= render :partial => ''comment'', :locals
=> {:comment =>
> comment } %>
>       <% end %>
>     </ul>
>   <% end %>
> </li>

-- 
Posted via http://www.ruby-forum.com/.