Accessing portal object trouble

Development Developing for Plone
,
#1

This week a faced a problem trying to access the portal object at the "schema definition scope". All what I was trying to do was reference an object from the portal to provide a link to it from the description of a dexterity field.

Right now i don't have the code anymore, but was something more or less like this:

def get_me_that_link(path):
  portal = api.portal.get()
  object = portal.restrictedTraverse(path)
  return object.absolute_url()


class IMySchema:
  fieldname = zope.schema(
    label=_(u'Field name'),
    description=_(u'<a href="{link}">More info</a>').format(link=get_me_that_link('/fs-mountpoint/plonesite/my-folder/my-basic-page')),
  )

I don't remember if it was exactly like that and if i write correct everything it's the main idea, but all was running ok, until I got an exception that tall me that zope (or plone, I don't remember) couldn't acces to the portal object, i read more about it, and i found that i could be cause running in debug mode, but i was in fg, anyway i tried to run it in normal mode and it was failing anyway.

#2

Your code is not going to work since the calculation is carried out during the startup phase of Zope/Plone and not at runtime. In particular such code would never ever work with multiple portals sharing the same code. To make it short: there is no functionality to calculate information for a dynamic description of a schema field at runtime.

-aj

#3

I know it wouldn't work on diferent portals, but instead of providing a static path i was thinking about read a registry from the portal where the user can specify where is his disclaimer page, so i can link it in the "i accept the terms of use" label.

Which would be the correct solution for a schema defined form?
Create a widget which renders the link? You'll have to create a widget for each kind of field you want to print a link on the label (chechbox, text, ...), which sounds kind of overkill

#4

It is possible (with some monkey patching). I did this for a customer some time ago (no Plone, but Zope3).

We defined a function which generates the description:

def lot_size_description():
    """Generate the description for the 'Lot Size' field.

    The description contains a mapping with the local ``authority_name`` which
    can vary between countries.

    :returns: Description text for the 'Lot Size' field.
    :rtype: string
    """
    loc_data = queryUtility(ILocationData)
    authority_name = loc_data.authority_name
    result = _(
        u'Enter the total area of the property in square meters. (e.g. '
        u'1225.32) Always cross-check data with ${authority_name}.', mapping={
            u'authority_name': authority_name,
        })
    return result

In the schema, no description is used:

class IListingDetails(Interface):
    """Listing Details"""
    lot_size = schema.Decimal(
        min=Decimal('0.01'),
        required=True,
        title=_(u'Total Lot Size'),
    )

We then applied a monkey patch to load the dynamic description:

#: Custom description for 'Total Lot Size'
IListingDetails.get('lot_size').description = listing.lot_size_description()
```
#5

It looks interesting, at which "point of execution"/file did you add the description in the interface's field?
And another question kind of offtopic, i see you use a parameter in the "_" function called "mapping", i guess it just works like the str's "format" method, but does the mapping parameter add some functionality to the i18n translation?

Thanks for your time!

#6

M[quote="Gerard, post:3, topic:4182"]
Which would be the correct solution for a schema defined form?Create a widget which renders the link? You'll have to create a widget for each kind of field you want to print a link on the label (chechbox, text, ...), which sounds kind of overkill
[/quote]

Correct solution...perhaps writing your own widget.
Quick and dirty: some Javascript modifying the DOM.

#7

The patches are loaded at the very end. Please take a look at the Monkey patching docs from Plone.

Yes, it adds a variable to the i18n message which will be replaced on runtime.

#8

Again, my solution is just a quick and dirty hack. Andreas point is totally valid and a custom widget would be the better solution.