Rendering nested elements with an arbitrary depth using Chameleon ZPT

Question

I am using Pyramid framework and I would like to render with Chameleon a html menu with nested lists (ul, li) of an arbitrary depth.

I cannot find some sort of recursive method in Chameleon in order to do so. It seems such a common need so I am wondering what is the right way of rendering nested elements with an arbitrary depth ?

But, there might be also some menu «widget» already available, fully tested and compatible with pyramid and Chamelon ?

Answer 1

<ul metal:define-macro="comment_list">
  <li tal:repeat="comment comments" class="comment" comment_id="${comment.id}">
    <div>ID: ${comment.id} ${comment.body}</div>
    <div tal:define="comments comment.children">
      <ul metal:use-macro="template.macros['comment_list']" />
    </div>
  </li>
</ul>

Answer 2

This is one answer to Graeme's question about the input to bismigalis' answer.

You'd start with a Comment object like this:

class Comment():                                                                                     

    id = 0                                                                                           
    body = ""                                                                                        
    children = []                                                                                    

    def __init__(self, id, body, children):                                                          
        self.id = id                                                                                 
        self.body = body                                                                             
        self.children = children

Then, you would create a list of comments and their children. For the sake of playing around, I just did this manually (sorry if it's not properly styled):

comments = []
comment1 = Comment(1, "First comment", None)
comment2 = Comment(2, "Second comment", [
        Comment(3, "Third comment", [
                Comment(5, "Fifth comment", None)
            ]
        ),
        Comment(4, "Fourth comment", None),
    ]
)

comment6 = Comment(6, "Sixth comment", None)

comments.append(comment1)
comments.append(comment2)
comments.append(comment6)

Then, you'd just make it a part of the returned dictionary from inside your view code:

return {'comments': comments}

The template code in bismagalis' answer will generate the following HTML:

        <ul>
          <li class="comment" comment_id="1">
            <div>ID: 1 First comment</div>
            <div>
              <ul>

        </ul>
            </div>
          </li>
          <li class="comment" comment_id="2">
            <div>ID: 2 Second comment</div>
            <div>
              <ul>
          <li class="comment" comment_id="3">
            <div>ID: 3 Third comment</div>
            <div>
              <ul>
          <li class="comment" comment_id="5">
            <div>ID: 5 Fifth comment</div>
            <div>
              <ul>

        </ul>
            </div>
          </li>
        </ul>
            </div>
          </li>
          <li class="comment" comment_id="4">
            <div>ID: 4 Fourth comment</div>
            <div>
              <ul>

        </ul>
            </div>
          </li>
        </ul>
            </div>
          </li>
          <li class="comment" comment_id="6">
            <div>ID: 6 Sixth comment</div>
            <div>
              <ul>

        </ul>
            </div>
          </li>
        </ul>

It appears there are quite a bit of extraneous <div> and <ul> tags mixed in there, so I may have missed something...