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| author | Chris McDonough <chrism@plope.com> | 2011-06-11 05:35:27 -0400 |
|---|---|---|
| committer | Chris McDonough <chrism@plope.com> | 2011-06-11 05:35:27 -0400 |
| commit | 99edc51a3b05309c7f5d98ff96289ec51b1d7660 (patch) | |
| tree | c8ddaa62b21c54eb996f5e375abd5bf9f5198806 /docs/narr/views.rst | |
| parent | df15ed98612e7962e3122da52d8d5f5b9d8882b2 (diff) | |
| download | pyramid-99edc51a3b05309c7f5d98ff96289ec51b1d7660.tar.gz pyramid-99edc51a3b05309c7f5d98ff96289ec51b1d7660.tar.bz2 pyramid-99edc51a3b05309c7f5d98ff96289ec51b1d7660.zip | |
- Pyramid now expects Response objects to have a __call__
method which implements the WSGI application interface
instead of the three webob attrs status, headerlist
and app_iter. Backwards compatibility exists for
code which returns response objects that do not
have a __call__.
- pyramid.response.Response is no longer an exception
(and therefore cannot be raised in order to generate
a response).
- Changed my mind about moving stuff from pyramid.httpexceptions
to pyramid.response. The stuff I moved over has been moved
back to pyramid.httpexceptions.
Diffstat (limited to 'docs/narr/views.rst')
| -rw-r--r-- | docs/narr/views.rst | 209 |
1 files changed, 88 insertions, 121 deletions
diff --git a/docs/narr/views.rst b/docs/narr/views.rst index 73a7c2e2a..990828f80 100644 --- a/docs/narr/views.rst +++ b/docs/narr/views.rst @@ -230,29 +230,29 @@ implements the :term:`Response` interface is to return a def view(request): return Response('OK') -You don't need to always use :class:`~pyramid.response.Response` to represent -a response. :app:`Pyramid` provides a range of different "exception" classes -which can act as response objects too. For example, an instance of the class -:class:`pyramid.response.HTTPFound` is also a valid response object -(see :ref:`http_exceptions` and ref:`http_redirect`). A view can actually -return any object that has the following attributes. - -status - The HTTP status code (including the name) for the response as a string. - E.g. ``200 OK`` or ``401 Unauthorized``. - -headerlist - A sequence of tuples representing the list of headers that should be - set in the response. E.g. ``[('Content-Type', 'text/html'), - ('Content-Length', '412')]`` - -app_iter - An iterable representing the body of the response. This can be a - list, e.g. ``['<html><head></head><body>Hello - world!</body></html>']`` or it can be a file-like object, or any - other sort of iterable. - -These attributes form the structure of the "Pyramid Response interface". +You don't need to use :class:`~pyramid.response.Response` to represent a +response. A view can actually return any object that has a ``__call__`` +method that implements the :term:`WSGI` application call interface. For +example, an instance of the following class could be successfully returned by +a view callable as a response object: + +.. code-block:: python + :linenos: + + class SimpleResponse(object): + def __call__(self, environ, start_response): + """ Call the ``start_response`` callback and return + an iterable """ + body = 'Hello World!' + headers = [('Content-Type', 'text/plain'), + ('Content-Length', str(len(body)))] + start_response('200 OK', headers) + return [body] + +:app:`Pyramid` provides a range of different "exception" classes which can +act as response objects too. For example, an instance of the class +:class:`pyramid.httpexceptions.HTTPFound` is also a valid response object +(see :ref:`http_exceptions` and ref:`http_redirect`). .. index:: single: view exceptions @@ -269,40 +269,8 @@ logged there. However, for convenience, a special set of exceptions exists. When one of these exceptions is raised within a view callable, it will always cause -:app:`Pyramid` to generate a response. Two categories of special exceptions -exist: internal exceptions and HTTP exceptions. - -Internal Exceptions -~~~~~~~~~~~~~~~~~~~ - -:exc:`pyramid.response.HTTPNotFound` and -:exc:`pyramid.response.HTTPForbidden` are exceptions often raised by Pyramid -itself when it (respectively) cannot find a view to service a request or when -authorization was forbidden by a security policy. However, they can also be -raised by application developers. - -If :exc:`~pyramid.response.HTTPNotFound` is raised within view code, the -result of the :term:`Not Found View` will be returned to the user agent which -performed the request. - -If :exc:`~pyramid.response.HTTPForbidden` is raised within view code, the -result of the :term:`Forbidden View` will be returned to the user agent which -performed the request. - -Both are exception classes which accept a single positional constructor -argument: a ``message``. In all cases, the message provided to the exception -constructor is made available to the view which :app:`Pyramid` invokes as -``request.exception.args[0]``. - -An example: - -.. code-block:: python - :linenos: - - from pyramid.response import HTTPNotFound - - def aview(request): - raise HTTPNotFound('not found!') +:app:`Pyramid` to generate a response. These are known as :term:`HTTP +exception` objects. .. index:: single: HTTP exceptions @@ -312,54 +280,77 @@ An example: HTTP Exceptions ~~~~~~~~~~~~~~~ -All classes documented in the :mod:`pyramid.response` module as inheriting -from the :class:`pryamid.response.Response` object implement the -:term:`Response` interface; an instance of any of these classes can be -returned or raised from within a view. The instance will be used as as the -view's response. +All classes documented in the :mod:`pyramid.httpexceptions` module documented +as inheriting from the :class:`pryamid.httpexceptions.HTTPException` are +:term:`http exception` objects. An instances of an HTTP exception object may +either be *returned* or *raised* from within view code. In either case +(return or raise) the instance will be used as as the view's response. -For example, the :class:`pyramid.response.HTTPUnauthorized` exception +For example, the :class:`pyramid.httpexceptions.HTTPUnauthorized` exception can be raised. This will cause a response to be generated with a ``401 Unauthorized`` status: .. code-block:: python :linenos: - from pyramid.response import HTTPUnauthorized + from pyramid.httpexceptions import HTTPUnauthorized def aview(request): raise HTTPUnauthorized() -A shortcut for importing and raising an HTTP exception is the -:func:`pyramid.response.abort` function. This function accepts an HTTP -status code and raises the corresponding HTTP exception. For example, to -raise HTTPUnauthorized, instead of the above, you could do: +An HTTP exception, instead of being raised, can alternately be *returned* +(HTTP exceptions are also valid response objects): .. code-block:: python :linenos: - from pyramid.response import abort + from pyramid.httpexceptions import HTTPUnauthorized def aview(request): - abort(401) - -This is the case because ``401`` is the HTTP status code for "HTTP -Unauthorized". Therefore, ``abort(401)`` is functionally equivalent to -``raise HTTPUnauthorized()``. Other exceptions in -:mod:`pyramid.response` can be raised via -:func:`pyramid.response.abort` as well, as long as the status code -associated with the exception is provided to the function. + return HTTPUnauthorized() -An HTTP exception, instead of being raised, can alternately be *returned* -(HTTP exceptions are also valid response objects): +A shortcut for creating an HTTP exception is the +:func:`pyramid.httpexceptions.responsecode` function. This function accepts +an HTTP status code and returns the corresponding HTTP exception. For +example, instead of importing and constructing a +:class:`~pyramid.httpexceptions.HTTPUnauthorized` response object, you can +use the :func:`~pyramid.httpexceptions.responsecode` function to construct +and return the same object. .. code-block:: python :linenos: - from pyramid.response import HTTPUnauthorized + from pyramid.httpexceptions import responsecode def aview(request): - return HTTPUnauthorized() + raise responsecode(401) + +This is the case because ``401`` is the HTTP status code for "HTTP +Unauthorized". Therefore, ``raise responsecode(401)`` is functionally +equivalent to ``raise HTTPUnauthorized()``. Documentation which maps each +HTTP response code to its purpose and its associated HTTP exception object is +provided within :mod:`pyramid.httpexceptions`. + +How Pyramid Uses HTTP Exceptions +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +HTTP exceptions are meant to be used directly by application application +developers. However, Pyramid itself will raise two HTTP exceptions at +various points during normal operations: +:exc:`pyramid.httpexceptions.HTTPNotFound` and +:exc:`pyramid.httpexceptions.HTTPForbidden`. Pyramid will raise the +:exc:`~pyramid.httpexceptions.HTTPNotFound` exception are raised when it +cannot find a view to service a request. Pyramid will raise the +:exc:`~pyramid.httpexceptions.Forbidden` exception or when authorization was +forbidden by a security policy. + +If :exc:`~pyramid.httpexceptions.HTTPNotFound` is raised by Pyramid itself or +within view code, the result of the :term:`Not Found View` will be returned +to the user agent which performed the request. + +If :exc:`~pyramid.httpexceptions.HTTPForbidden` is raised by Pyramid itself +within view code, the result of the :term:`Forbidden View` will be returned +to the user agent which performed the request. .. index:: single: exception views @@ -369,11 +360,10 @@ An HTTP exception, instead of being raised, can alternately be *returned* Custom Exception Views ---------------------- -The machinery which allows :exc:`~pyramid.response.HTTPNotFound`, -:exc:`~pyramid.response.HTTPForbidden` and other responses to be used as -exceptions and caught by specialized views as described in -:ref:`special_exceptions_in_callables` can also be used by application -developers to convert arbitrary exceptions to responses. +The machinery which allows HTTP exceptions to be raised and caught by +specialized views as described in :ref:`special_exceptions_in_callables` can +also be used by application developers to convert arbitrary exceptions to +responses. To register a view that should be called whenever a particular exception is raised from with :app:`Pyramid` view code, use the exception class or one of @@ -409,8 +399,8 @@ raises a ``helloworld.exceptions.ValidationFailure`` exception: Assuming that a :term:`scan` was run to pick up this view registration, this view callable will be invoked whenever a ``helloworld.exceptions.ValidationFailure`` is raised by your application's -view code. The same exception raised by a custom root factory or a custom -traverser is also caught and hooked. +view code. The same exception raised by a custom root factory, a custom +traverser, or a custom view or route predicate is also caught and hooked. Other normal view predicates can also be used in combination with an exception view registration: @@ -458,57 +448,34 @@ Exception views can be configured with any view registration mechanism: Using a View Callable to Do an HTTP Redirect -------------------------------------------- -Two methods exist to redirect to another URL from within a view callable: a -short form and a long form. The short form should be preferred when -possible. - -Short Form -~~~~~~~~~~ - -You can issue an HTTP redirect from within a view callable by using the -:func:`pyramid.response.redirect` function. This function raises an -:class:`pyramid.response.HTTPFound` exception (a "302"), which is caught by -the default exception response handler and turned into a response. - -.. code-block:: python - :linenos: - - from pyramid.response import redirect - - def myview(request): - redirect('http://example.com') - -Long Form -~~~~~~~~~ - -You can issue an HTTP redirect from within a view "by hand" instead of -relying on the :func:`pyramid.response.redirect` function to do it for -you. +You can issue an HTTP redirect by using the +:class:`pyramid.httpexceptions.HTTPFound` class. Raising or returning an +instance of this class will cause the client to receive a "302 Found" +response. -To do so, you can *return* a :class:`pyramid.response.HTTPFound` +To do so, you can *return* a :class:`pyramid.httpexceptions.HTTPFound` instance. .. code-block:: python :linenos: - from pyramid.response import HTTPFound + from pyramid.httpexceptions import HTTPFound def myview(request): return HTTPFound(location='http://example.com') -Or, alternately, you can *raise* an HTTPFound exception instead of returning -one. +Alternately, you can *raise* an HTTPFound exception instead of returning one. .. code-block:: python :linenos: - from pyramid.response import HTTPFound + from pyramid.httpexceptions import HTTPFound def myview(request): raise HTTPFound(location='http://example.com') -The above form of generating a response by raising HTTPFound is completely -equivalent to ``redirect('http://example.com')``. +When the instance is raised, it is caught by the default :term:`exception +response` handler and turned into a response. .. index:: single: unicode, views, and forms |