From 7e2c6cbb452aa986891b2a99653a147bfb053e19 Mon Sep 17 00:00:00 2001
From: Chris McDonough <chrism@agendaless.com>
Date: Mon, 1 Sep 2008 01:52:14 +0000
Subject:   - New API module: ``repoze.bfg.view``.  This module contains the
 functions     named ``render_view_to_response``, ``render_view_to_iterable``
 and     ``is_response``, which are documented in the API docs.  These
 features     aid programmatic (non-request-driven) view execution.

---
 repoze/bfg/view.py | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 repoze/bfg/view.py

(limited to 'repoze/bfg/view.py')

diff --git a/repoze/bfg/view.py b/repoze/bfg/view.py
new file mode 100644
index 000000000..180c020a0
--- /dev/null
+++ b/repoze/bfg/view.py
@@ -0,0 +1,71 @@
+from zope.component import queryMultiAdapter
+from zope.component import queryUtility
+
+from repoze.bfg.interfaces import ISecurityPolicy
+from repoze.bfg.interfaces import IViewPermission
+from repoze.bfg.interfaces import IView
+from repoze.bfg.security import Unauthorized
+
+def render_view_to_response(context, request, name='', secure=True):
+    """ Render the view named ``name`` against the specified
+    ``context`` and ``request`` to an object implementing
+    ``repoze.bfg.interfaces.IResponse`` or ``None`` if no such view
+    exists.  This function will return ``None`` if a corresponding
+    view cannot be found.  If ``secure`` is ``True``, and the view is
+    protected by a permission, the permission will be checked before
+    calling the view function.  If the permission check disallows view
+    execution (based on the current security policy), a
+    ``repoze.bfg.security.Unauthorized`` exception will be raised; its
+    ``message`` attribute explains why the view access was disallowed.
+    If ``secure`` is ``False``, no permission checking is done."""
+    if secure:
+        security_policy = queryUtility(ISecurityPolicy)
+        if security_policy:
+            permission = queryMultiAdapter((context, request), IViewPermission,
+                                           name=name)
+            if permission is not None:
+                result = permission(security_policy)
+                if not result:
+                    raise Unauthorized(result)
+    return queryMultiAdapter((context, request), IView, name=name)
+
+def render_view_to_iterable(context, request, name='', secure=True):
+    """ Render the view named ``name`` against the specified
+    ``context`` and ``request``, and return an iterable representing
+    the view response's ``app_iter`` (see the interface named
+    ``repoze.bfg.interfaces.IResponse``).  This function will return
+    ``None`` if a corresponding view cannot be found.  Additionally,
+    this function will raise a ``ValueError`` if a view function is
+    found and called but the view does not return an object which
+    implements ``repoze.bfg.interfaces.IResponse``.  You can usually
+    get the string representation of the return value of this function
+    by calling ``''.join(iterable)``.  If ``secure`` is ``True``, and
+    the view is protected by a permission, the permission will be
+    checked before calling the view function.  If the permission check
+    disallows view execution (based on the current security policy), a
+    ``repoze.bfg.security.Unauthorized`` exception will be raised; its
+    ``message`` attribute explains why the view access was disallowed.
+    If ``secure`` is ``False``, no permission checking is done."""
+    response = render_view_to_response(context, request, name, secure)
+    if response is None:
+        return None
+    if not is_response(response):
+        raise ValueError('response did not implement IResponse: %r' % response)
+    return response.app_iter
+
+def is_response(ob):
+    """ Return True if ``ob`` implements the
+    ``repoze.bfg.interfaces.IResponse`` interface, False if not.  Note
+    that this isn't actually a true Zope interface check, it's a
+    duck-typing check, as response objects are not obligated to
+    actually implement a Zope interface."""
+    # response objects aren't obligated to implement a Zope interface,
+    # so we do it the hard way
+    if ( hasattr(ob, 'app_iter') and hasattr(ob, 'headerlist') and
+         hasattr(ob, 'status') ):
+        if ( hasattr(ob.app_iter, '__iter__') and
+             hasattr(ob.headerlist, '__iter__') and
+             isinstance(ob.status, basestring) ) :
+            return True
+    return False
+
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