===================================
25: Adding Resources To Hierarchies
===================================

Multiple views per type allowing addition of content anywhere in a
resource tree.

Background
==========

We now have multiple kinds-of-things, but only one view per resource
type. We need the ability to add things to containers,
then view/edit resources.

This introduces the concept of named views. A name is a part of the URL
that appears after the resource identifier. For example::

  @view_config(context=Folder, name='add_document')

...means that this URL::

  http://localhost:6543/some_folder/add_document

...will match the view being configured. It's as if you have an
object-oriented web, with operations on resources represented by a URL.

When you omit the ``name=`` (as we did in the previous examples,
you are establishing a "default view" for the context. That is,
a view to be used when no view name is found during traversal.

Goals
=====

- Adding and editing content in a resource tree

- Simple form which POSTs data

- A view which takes the POST data, creates a resource, and redirects
  to the newly-added resource

- Named views

Steps
=====

#. We are going to use the previous step as our starting point:

   .. code-block:: bash

    (env27)$ cd ..; cp -r traversal_typeviews traversal_addcontent; cd traversal_addcontent
    (env27)$ python setup.py develop


#. Our views in ``traversal_addcontent/tutorial/views.py`` need
   type-specific registrations:

   .. literalinclude:: traversal_addcontent/tutorial/views.py
      :linenos:

#. One small change in
   ``traversal_addcontent/tutorial/templates/document.pt``:

   .. literalinclude:: traversal_addcontent/tutorial/templates/document.pt
      :language: html
      :linenos:

#. Need forms added to
   ``traversal_addcontent/tutorial/templates/folder.pt``:

   .. literalinclude:: traversal_addcontent/tutorial/templates/folder.pt
      :language: html
      :linenos:

#. Forms also needed for
   ``traversal_addcontent/tutorial/templates/site.pt``:

   .. literalinclude:: traversal_addcontent/tutorial/templates/site.pt
      :language: html
      :linenos:

#. ``$ nosetests`` should report running 4 tests.

#. Run your Pyramid application with:

   .. code-block:: bash

    (env27)$ pserve development.ini --reload

#. Open ``http://localhost:6543/`` in your browser.

Analysis
========

Our views now represent a richer system, where form data can be
processed to modify content in the tree. We do this by attaching named
views to resource types, giving them a natural system for
object-oriented operations.

To enforce uniqueness, we randomly choose a satisfactorily large number.

Extra Credit
============

#. Can ``document_view`` simply return nothing instead of an empty
   dictionary?