megrok.pagetemplate 0.5

Page template component for Grok, based on zope.pagetemplate

Introduction

megrok.pagetemplate is a thin Grok layer above zope.pagetemplate package. It allows the developper to register IPageTemplate components using grokked components. The syntax is meant to be very simple and readable. megrok.pagetemplate only provides one component named PageTemplate and uses the basic grokcore.view and grokcore.viewlet directives : name, view, context, layer. To make it even simplier and straightforward, it uses the grokcore.view template registry to register the template files associated to the pagetemplate component.

Getting started

First, we import our dependencies:

>>> import grokcore.view as view
>>> import megrok.pagetemplate as pt
>>> from grokcore.component.testing import grok, grok_component

A complete yet self-explanatory example

To get started with the code itself, let’s explain the concept behind the PageTemplate component. The display is usually handled by the a dedicated component: the View. The View is a multi adapter, adapting the context and the request. It provides a rendering method (__call__, usually). If we want to customize a View, we need to subclass it or override it. In both case, we end up with a new View and some code might have to be duplicated.

The PageTemplate component allows you to interact at the rendering level. This new component implements the zope.pagetemplate IPageTemplate interface and is registered as a multi adapter, adapting a View and a Layer (request type). This PageTemplate can be named, for more customization possibilities.

Let’s build a concrete example to get into the concept. First, we need a context. Our usecase will be to provide different renderings for an adorable animal : the Mammoth. First, let’s create our mammoth and a simple view that displays it:

>>> from zope.component import getMultiAdapter
>>> from zope.pagetemplate.interfaces import IPageTemplate

>>> class Mammoth(view.Context):
...     """A furry pachyderm
...     """
...     nickname = u"Grokky"


>>> class MammothView(view.View):
...     """A view that display a mammoth
...     """
...     view.context(Mammoth)
...
...     def update(self):
...         self.mammoth_name = u"My name is %s." % self.context.nickname
...
...     def render(self):
...         template = getMultiAdapter((self, self.request), IPageTemplate)
...         return template()

>>> grok_component('my_mammoth_view', MammothView)
True

As we can see here, the View render method is a call to the PageTemplate component. It will render the template found by the registry lookup.

To be complete, here, we’ll provide a IPageTemplate component:

>>> class NakedMammoth(pt.PageTemplate):
...     """A mammoth shown in its simpliest apparel
...     """
...     pt.view(MammothView)
...     template = view.PageTemplate(
...        '<span tal:replace="view/mammoth_name" /> I am naked !'
...        )

>>> grok_component('NakedMammoth', NakedMammoth)
True

Now that our template is registered, we can try to summon the view and to render it:

>>> from zope.publisher.browser import TestRequest
>>> request = TestRequest()
>>> mammoth = Mammoth()

>>> mnv = getMultiAdapter((mammoth, request), name="mammothview")
>>> print mnv()
My name is Grokky. I am naked !
<BLANKLINE>

Our Mammoth is rendered as expected. Though, we cannot decently leave this creature naked. It needs some fur to face the harsh temperature of the Siberian winter.

In order to customize our Mammoth rendering, to change it from Naked to Furry, we’ll create a skin on which we’ll register our new ‘furry’ template component:

>>> from zope.publisher.interfaces import browser
>>> class IFurryLayer(browser.IDefaultBrowserLayer):
...     """A layer for furry animals.
...     """
>>> furry_request = TestRequest(skin=IFurryLayer)


>>> class FurryMammoth(pt.PageTemplate):
...     """A mammoth shown in its simpliest apparel
...     """
...     pt.view(MammothView)
...     pt.layer(IFurryLayer)
...     template = view.PageTemplate(
...        '<span tal:replace="view/mammoth_name" /> I am all furry !'
...        )

>>> grok_component('FurryMammoth', FurryMammoth)
True

Our new template registered, we are now able to test if everything worked as intended. Using the new skin, our Mammoth should now be furry:

>>> mfv = getMultiAdapter((mammoth, furry_request), name="mammothview")
>>> print mfv()
My name is Grokky. I am all furry !
<BLANKLINE>

Note - we can query our component with a very convenient function:

>>> print pt.getPageTemplate(mfv, furry_request)
<megrok.pagetemplate.components.ViewPageTemplate object at ...>

Awesome. Our Mammoth is now fully prepared to face the cold. Though, let’s make sure the simpliest request strip the animal from its warm hairs:

>>> mnv = getMultiAdapter((mammoth, request), name="mammothview")
>>> print mnv()
My name is Grokky. I am naked !
<BLANKLINE>

That works. Enjoy !

Changelog

0.5 (2010-05-27)

• Cleaned up the code to respect the strict pep8. Removed unused imports.

• Tested for Grok 1.1

0.4.1 (2010-02-22)

• The MANIFEST has been updated so the ‘templates’ folder of the tests module is now part of the source release (thus the tests now run correctly).

0.4 (2010-02-21)

• Cleaned up the dependencies, to get rid of all the zope.app artifacts.

• Cleaned up the imports and tests.

0.3 - Beta3 Release

• Modified tests to import all the directives needed directly from the package megrok.pagetemplate itself. [trollfot]

• Added a convenient function getPageTemplate to query the page template component.

0.2 - Beta2 Release

• megrok.pagetemplate has been upgraded to work with the latest grokcore.view (1.12.1). Tests has been corrected and CodeView is gone. [trollfot]

0.1 - Beta1 Release

• Initial release [trollfot]