Dolmen Layout/View Selector
Project description
The package dolmen.app.viewselector is an extension for Dolmen applications, allowing a basic management of alternative views.
About
In a CMS, it’s often very useful to be able to design and provide several views for a single item. These views can be relevant, according to a given context and situation. dolmen.app.viewselector allows you to define a view as being an “alternate” option to render a given context. A menu then provides you the machinery to select the most relevant view for your usecase.
A quick overview
To know that a component can provide alternative views, we need to explicitly specify it. An interface defines the “selector” capability:
>>> from dolmen.app.viewselector import IViewSelector >>> list(IViewSelector) ['selected_view'] >>> IViewSelector['selected_view'] <...TextLine...>
The IViewSelector interface defines a single field, known as ‘selected_view’. The field value is merely the name of the Page component currently used:
>>> IViewSelector['selected_view'].default u'base_view'
Out of the box, the default value is set to ‘base_view’.
Defining the content
To demonstrate the alternative views, we first need a context that is aware of the views selection:
>>> from zope.location import Location >>> from zope.interface import implements >>> class Bear(Location): ... implements(IViewSelector) ... selected_view = u"sleeping"
We defined the default view to the view named “sleeping”.
Defining alternate views
The alternative views are ‘pages’ (see megrok.layout and dolmen.app.layout) that are registered onto a dedicated menu. To define an alternative view, we inherit from the AlternativeView base class:
>>> import grokcore.view as grok >>> from grokcore.component import testing >>> from dolmen.app.viewselector import AlternativeView >>> class Sleeping(AlternativeView): ... grok.context(Bear) ... grok.title("Sleeping bear") ... ... def render(self): ... return u"RRrrr..." >>> testing.grok_component('sleeping', Sleeping) True
The “sleeping” view that we defined as a default value for our IViewSelector is now defined and registered. Let’s register 2 other views, to populate the menu and provide a “realistic” usecase:
>>> class PolarFur(AlternativeView): ... grok.context(Bear) ... grok.title("Polar bear") ... ... def render(self): ... return u"I'm white !" >>> testing.grok_component('polar', PolarFur) True >>> class SpringFur(AlternativeView): ... grok.context(Bear) ... grok.title("Spring bear") ... grok.require("dolmen.content.Edit") ... ... def render(self): ... return u"I'm brown !" >>> testing.grok_component('spring', SpringFur) True
Default dynamic index
In order to render the selected view, another view is used. We may call it a “routing” view, as it’s used to lookup and render the desired component.
We first need to instance the two needed components, the content and the request
>>> from zope.publisher.browser import TestRequest >>> herman = Bear() >>> request = TestRequest()
The content provides IViewSelector, the interface for which the “routing” view is registered:
>>> IViewSelector.providedBy(herman) True
The “routing” view is by convention called “index” and can be looked up as a basic view:
>>> from zope.component import getMultiAdapter >>> index = getMultiAdapter((herman, request), name="index") >>> index <dolmen.app.viewselector.select.SelectedView...>
This view, when rendered, will look up and render the view named as the selected_view attribute, registered for the same content and request:
>>> herman.selected_view u'sleeping' >>> index.render() u'RRrrr...'
If we set a different value for the selected_view attribute, the looked up view changes accordingly:
>>> herman.selected_view = u"polarfur" >>> index.render() u"I'm white !" >>> herman.selected_view = u"springfur" >>> index.render() u"I'm brown !"
If the view doesn’t exist, a base message is returned:
>>> herman.selected_view = u"nothing" >>> index.render() u'The selected view is not a valid IPage component.'
Applying the view via the User interface
The selected view can be chosen from a list of available alternative view. This choice is made via a menu, for which the views are registered.
Apply
The menu above exposes the view ‘viewselector’, registered for a IViewSelector content. This view is the component that effectively changes the selected_view attribute to the clicked value.
Let’s simulate a click to test that view. The current value of the selected_view attribute is inconsistant:
>>> herman.selected_view u'nothing'
We want it changed to something existing, like the PolarFur view:
>>> request = TestRequest(form={'name': u'polarfur'}) >>> handler = getMultiAdapter((herman, request), name="viewselector") >>> handler <dolmen.app.viewselector.select.ApplyView ...>
Logged in as an admin user, we can apply the selected view:
>>> login('zope.mgr', request) >>> handler() 'http://127.0.0.1/herman'
The view redirects you to the base view of the content. The value is now changed:
>>> herman.selected_view u'polarfur'
Changes
0.2.1 (2010-05-31)
Fixed the egg dist, by removing the zip-safe flag.
0.2 (2010-03-26)
Fixed missing MANIFEST.
0.1 (2010-03-25)
Initial release.
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