Custom TALES extensionsΒΆ
+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)
+