[Zope] [ZDP] Tree FAQs

[Martijn Pieters]

My two cents on the tree tag:

* How do I tell the tree tag to show only Folders?

    By using the objectValues function in the branches_expr attribute of
    the tree tag. The objectValues function of a folder returns all objects
    contained by that folder. 

    You can however, specify a list of object metatypes that it should
    return. objectValues(['DTML Document']) will only return all DTML 
    Document objects in a Folder. Other metatypes you could select on are:
    Folder, DTML Method, File, Image, Mail Host, User Folder and Session.
    This is not a complete list, as Products can and will define their own
    metatypes. If you want to show more types, just add them to the list,
    like objValues(['Image', 'File']).
    
    Example of a Folder tree (with links to them)::

        <!--#tree branches_expr="objectValues(['Folder'])"-->
	    <A HREF="<!--#var URL1-->/<!--#var id-->">
            <!--#var title_or_id-->
            </A>
	<!--#/tree-->

* How can I collapse or expand a tree using a URL?

    The tree tag will show a tree fully expanded when the 'expand_all'
    variable is present in its namespace. So when a URL, showing a tree, is
    called with ?expand_all=1, the tree tag will expand all it's branches.
    Collapsing can be achieved with collapse_all.

    The following example shows a tree with collapse and expand 'buttons'::

        <A HREF="<!--#var URL0-->?expand_all=1">
          Expand all</A>|
        <A HREF="<!--#var URL0-->?collapse_all=1">
          Collapse all</A>

        <!--#tree--><!--#var id--><!--#/tree-->

* How can I limit a tree to showing only *one* branch at a time?

    Use the 'single' attribute for your tree, like in::

        <!--#tree single--><!--#var id--><!--#/tree-->


More cents will follow.

Martijn


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M.J. Pieters, Web Developer
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