Custom TALES extensions¶
-PyAMS defines a custom expression for TALES called extension.
-When this expression is encountered, the renderer is looking for an
-ITALESExtension
-multi-adapter for the current context, request and view, for the current
-context and request, or only for the current context, in this order.
-If an adapter is found, the renderer call it’s render() method with
-the expression parameters as input parameters.
For example, the metas extension is an ITALESExtension adapter defined into
-pyams_skin.metas module which can be used to include all required headers in
-a page template. Extension is used like this in the page layout template:
<tal:var replace="structure extension:metas" />
-This extension is defined like this:
-from pyams_skin.interfaces.metas import IHTMLContentMetas
-from pyams_utils.interfaces.tales import ITALESExtension
-from pyramid.interfaces import IRequest
-
-from pyams_utils.adapter import adapter_config, ContextRequestViewAdapter
-
-@adapter_config(name='metas', context=(Interface, IRequest, Interface), provides=ITALESExtension)
-class MetasTalesExtension(ContextRequestViewAdapter):
- '''extension:metas TALES extension'''
-
- def render(self, context=None):
- if context is None:
- context = self.context
- result = []
- for name, adapter in sorted(self.request.registry.getAdapters((context, self.request, self.view),
- IHTMLContentMetas),
- key=lambda x: getattr(x[1], 'order', 9999)):
- result.extend([meta.render() for meta in adapter.get_metas()])
- return '\n\t'.join(result)
-Some TALES extensions can require or accept arguments. For example, the absolute_url extension can accept -a context and a view name:
-<tal:var define="logo config.logo">
- <img tal:attributes="src extension:absolute_url(logo, '++thumb++200x36.png');" />
-</tal:var>
-The extension is defined like this:
-from persistent.interfaces import IPersistent
-from pyams_utils.interfaces.tales import ITALESExtension
-
-from pyams_utils.adapter import adapter_config, ContextRequestViewAdapter
-from pyramid.url import resource_url
-from zope.interface import Interface
-
-@adapter_config(name='absolute_url', context=(IPersistent, Interface, Interface), provides=ITALESExtension)
-class AbsoluteUrlTalesExtension(ContextRequestViewAdapter):
- '''extension:absolute_url(context, view_name) TALES extension'''
-
- def render(self, context=None, view_name=None):
- if context is None:
- context = self.context
- return resource_url(context, self.request, view_name)
-