[Zope-dev] Re: [Zope] Object Links/references and Zope 2.6

8 Mar 2002

      Hi:

  Regarding my previous proposal.....
...
I would like to propose my "Paste Reference"/symlink hack for
inclusion into Zope 2.6
And referring to my previous msg.....

At 19:04 07-08-2001 +0100, Mario Valente wrote:
...
As discussed previously by others (re: object references) and
asked by myself: I had the need to be able to refer to objects
from different points of the folder hierarchy without duplicating
those objects.

...
- edited CopySupport.py
 - copied the manage_pasteObjects method to a manage_pasteMonikers
   method
 - commented the #ob=ob._getCopy(self)  line  (the duplicate object part)
 - added a "Paste Ref" button to the lib/python/OFS/dtml/main.dtml file that
   calls the pasteMonikers method
"""
 <input class="form-element" type="submit"
name="manage_pasteMonikers:method"
  value="Paste Ref." />
 """
...
Issues/TODO
- find a way to distinguish references from the original (tried to change
   the meta_type at paste time but no luck). At least the meta_type/icon
should
   change to provide a visual cue.
  - provide tool(s) to find impact of changing a reference. Provide a link
from a
   reference object to the original. Provide a link from an object to its
several
   references.
I have now solved the issues/TODO. I now have implemented a way
 to distinguish references from the original. Links have a name like
 "copy_of_XXXX" but instead its "shortcut_to_XXX" and they also have
 a different metatype and a different icon. There's also crude management
 screens to get to the original object.

  Here's the *major* hack :-) (its such a kludge that even I am shocked :-)
  But it serves to demonstrate the purpose.

  Like previously described I edited CopySupport.py and created a
 new method called pasteMonikers. This method is accessed by the
 interface button referred above.

  The coding difference is that this method now creates a *new* object
 (instead of copying the old one, which is the semantics of usual Copy/Paste,
  and instead of using the original object, which is the semantics of the
  PasteReference I created and described before).

  This is the relevant piece of code:

                #ob=ob._getCopy(self)

                id=self._get_linkid(ob.getId())
                ob = SimpleItem.ItemShortcut(ob)
                ob._setId(id)

                self._setObject(id, ob)

                ob = self._getOb(id)
                ob.manage_afterClone(ob)

  As you can see a new id is created for the new object (method 
 _get_linkid is identical to method get_id but returns ids with the
 format "shortcut_to_%s") and a new object of class ItemShortcut
 is created and pasted into the current folder.

  The ItemShortcut class was created at the SimpleItem.py file
 and its basically a Proxy pattern.
  This is the relevant code, added at the end of SimpleItem.py:

class ItemShortcut(SimpleItem):
        """Proxying class for shortcut implementation
        """
        meta_type = "Shortcut"
        icon     ='shortcut.gif'

        manage_options= SimpleItem.manage_options + (
        {'label':'View',
         'action':'index_html',
         'help':''},
        )
        manage_options= SimpleItem.manage_options + (
        {'label':'Properties',
         'action':'manage_properties',
         'help':''},
        )
        #__ac_permissions__=(('View', ()),)
        __ac_permissions__=(('View', ('__call__', '')),)

        def __init__(self, obj=None):
                self.__obj__ = obj

        def __repr__(self):
                return "Proxy for "+`self.__obj__`

        def index_html(self):
                """Proxying class for shortcut implementation
                """
                return self.__obj__.__call__()

        def manage_properties(self):
                """Proxying class for shortcut implementation
                """
                return """<HTML><head></head>
                        <body>
                        Shortcut for """+`self.__obj__`+"""
                        <p>
                        <a href="""+`self.__obj__.absolute_url()`+""">View
original object</a>
                        <p>
                        <a
href="""+self.__obj__.absolute_url()+"""/manage_workspace>Edit original
object</a>
                        </body></html>"""

   Once again, this is just proof of concept, and should be correctly
 (read 'nicely' :-) implemented for Zope 2.6.

  C U!

  -- Mario Valente