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A widget for z3c.relationfield.

Project Description

This package implements a zope.formlib compatible widget for relations as defined by z3c.relationfield.

This package does not provide a z3c.form widget for z3c.relationfield, but it is hoped that will eventually be developed as well (in another package).


In order to demonstrate our widget, we need to first set up a relation field (for the details of this see z3c.relationfield’s documentation):

>>> from z3c.relationfield import Relation
>>> from zope.interface import Interface
>>> class IItem(Interface):
...   rel = Relation(title=u"Relation")
>>> from z3c.relationfield.interfaces import IHasRelations
>>> from persistent import Persistent
>>> from zope.interface import implements
>>> class Item(Persistent):
...   implements(IItem, IHasRelations)
...   def __init__(self):
...     self.rel = None
>>> from import SiteManagerContainer
>>> from import BTreeContainer
>>> class TestApp(SiteManagerContainer, BTreeContainer):
...   pass

Set up the application with the right utilities:

>>> root = getRootFolder()['root'] = TestApp()
>>> from import LocalSiteManager
>>> root.setSiteManager(LocalSiteManager(root))
>>> from import setSite
>>> setSite(root)
>>> from import IntIds
>>> from import IIntIds
>>> root['intids'] = intids = IntIds()
>>> sm = root.getSiteManager()
>>> sm.registerUtility(intids, provided=IIntIds)
>>> from z3c.relationfield import RelationCatalog
>>> from zc.relation.interfaces import ICatalog
>>> root['catalog'] = catalog = RelationCatalog()
>>> sm.registerUtility(catalog, provided=ICatalog)

Items a and b with a relation from b to a:

>>> root['a'] = Item()
>>> from z3c.relationfield import RelationValue
>>> b = Item()
>>> from zope import component
>>> from import IIntIds
>>> intids = component.getUtility(IIntIds)
>>> a_id = intids.getId(root['a'])
>>> b.rel = RelationValue(a_id)
>>> root['b'] = b

We also need to set up a utility that knows how to generate an object path for a given object, and back:

>>> import grokcore.component as grok
>>> from z3c.objpath.interfaces import IObjectPath
>>> class ObjectPath(grok.GlobalUtility):
...   grok.provides(IObjectPath)
...   def path(self, obj):
...       return obj.__name__
...   def resolve(self, path):
...       try:
...           return root[path]
...       except KeyError:
...           raise ValueError("Cannot resolve: %s" % path)
>>> grok.testing.grok_component('ObjectPath', ObjectPath)

Let’s also set up a broken relation:

>>> d = root['d'] = Item()
>>> d_id = intids.getId(root['d'])
>>> c = Item()
>>> c.rel = RelationValue(d_id)
>>> root['c'] = c
>>> del root['d']
>>> root['c'].rel.to_object is None
>>> root['c'].rel.isBroken()

The relation widget

The relation widget can be looked up for a relation field. The widget will render with a button that can be used to set the relation. Pressing this button will show a pop up window. The URL implementing the popup window is defined on a special view that needs to be available on the context object (that the relation is defined on). This view must be named “explorerurl”. We’ll provide one here:

>>> from zope.interface import Interface
>>> import grokcore.view
>>> class ExplorerUrl(grokcore.view.View):
...   grok.context(Interface)
...   def render(self):
...      return ''

Now we can Grok the view:

>>> grok.testing.grok_component('ExplorerUrl', ExplorerUrl)

Let’s take a look at the relation widget now:

>>> from zope.publisher.browser import TestRequest
>>> from z3c.relationfieldui import RelationWidget
>>> request = TestRequest()
>>> field = IItem['rel']
>>> bound = field.bind(root['b'])
>>> widget = RelationWidget(bound, request)
>>> widget.setRenderedValue(bound.get(root['b']))
>>> print widget()
<input class="textType" id="field.rel" name="field.rel" size="20" type="text" value="a"  /><input class="buttonType" onclick="Z3C.relation.popup(this.previousSibling, ';from_path=b')" type="button" value="get relation" />

Let’s also try it with the broken relation:

>>> bound = field.bind(root['c'])
>>> widget = RelationWidget(bound, request)
>>> widget.setRenderedValue(bound.get(root['c']))

When we render the widget, the value is still correct (even though it’s broken):

>>> print widget()
<input class="textType" id="field.rel" name="field.rel" size="20" type="text" value="d"  /><input class="buttonType" onclick="Z3C.relation.popup(this.previousSibling, ';from_path=c')" type="button" value="get relation" />

Relation Choice

Let’s examine the RelationChoice field from z3c.relationfield. We need to provide a source of possible relations for it, and we can do this using the RelationSourceFactory:

>>> from z3c.relationfieldui import RelationSourceFactory
>>> class MyRelationSourceFactory(RelationSourceFactory):
...    def getTargets(self):
...        return [root['a'], root['b'], root['c']]

In the source, we simply return an iterable of objects that are possible relation targets.

Let’s now create an object that makes use of this source:

>>> from z3c.relationfield import RelationChoice
>>> class IItemChoice(Interface):
...   rel = RelationChoice(title=u"Relation", required=False,
...                        source=MyRelationSourceFactory())

We can now take a look at the widget, using ChoiceInputWidget:

>>> from import ChoiceInputWidget

>>> class ItemChoice(Persistent):
...   implements(IItemChoice, IHasRelations)
...   def __init__(self):
...     self.rel = None

>>> root['choice_a'] = ItemChoice()
>>> field = IItemChoice['rel']
>>> bound = field.bind(root['choice_a'])
>>> widget = ChoiceInputWidget(bound, request)

Let’s first render the widget without a particular rendered value set:

>>> print widget()
<div class="value">
<select id="field.rel" name="field.rel" size="1" >
<option selected="selected" value="">(no value)</option>
<option value="a">a</option>
<option value="b">b</option>
<option value="c">c</option>
<input name="field.rel-empty-marker" type="hidden" value="1" />

Let’s try it again with a value set as a relation to a:

>>> choice_b = ItemChoice()
>>> choice_b.rel = RelationValue(a_id)
>>> root['choice_b'] = choice_b
>>> bound = field.bind(root['choice_b'])
>>> widget = ChoiceInputWidget(bound, request)
>>> widget.setRenderedValue(bound.get(root['b']))

When we look at the widget we see that this relation is indeed selected:

>>> print widget()
<div class="value">
<select id="field.rel" name="field.rel" size="1" >
<option value="">(no value)</option>
<option selected="selected" value="a">a</option>
<option value="b">b</option>
<option value="c">c</option>
<input name="field.rel-empty-marker" type="hidden" value="1" />

Relation display widget

The display widget for relation will render a URL to the object it relates to. What this URL will be exactly can be controlled by defining a view on the object called “relationurl”. Without such a view, the display widget will link directly to the object:

>>> from z3c.relationfieldui import RelationDisplayWidget
>>> bound = field.bind(root['b'])
>>> widget = RelationDisplayWidget(bound, request)
>>> widget.setRenderedValue(bound.get(root['b']))

The widget will point to the plain URL of rel’s to_object:

>>> print widget()
<a href="">a</a>

Now we register a special relationurl view:

>>> class RelationUrl(grokcore.view.View):
...   grok.context(Interface)
...   def render(self):
...      return self.url('edit')
>>> grok.testing.grok_component('RelationUrl', RelationUrl)

We should now see a link postfixed with /edit:

>>> print widget()
<a href="">a</a>

When the relation is broken, it will still display, but as broken:

>>> bound = field.bind(root['c'])
>>> widget = RelationDisplayWidget(bound, request)
>>> widget.setRenderedValue(bound.get(root['c']))
>>> print widget()
Broken relation to: d


0.5 (2009-02-10)

  • Add support for RelationChoice field. To create a relation field that uses a drop-down list to select the relation target, implement a RelationSourceFactory (implement the getTargets method), and pass it as a source to RelationChoice.

0.4 (2009-01-20)

  • Use improved z3c.relationfield to better handle broken relations. Broken relations are now accepted by the UI but will be stored as broken.

0.3 (2009-01-16)

  • Pass along from_attribute and from_path URL parameters to explorer_url.

0.2 (2009-01-08)

  • Update the value of the input field using .value instead of using setAttribute('value', ...). The latter did not update dynamically updated input fields, and the former does.
  • z3c.relationfield does not use IRelationInfo anymore and instead exposes create_relation. Use this instead.

0.1.1 (2008-12-10)

  • Small internet Explorer compatibility tweaks.

0.1 (2008-12-05)

  • Initial public release.


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