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diff --git a/docs/quick_tutorial/json.rst b/docs/quick_tutorial/json.rst new file mode 100644 index 000000000..213de8364 --- /dev/null +++ b/docs/quick_tutorial/json.rst @@ -0,0 +1,101 @@ +======================================== +14: Ajax Development With JSON Renderers +======================================== + +Modern web apps are more than rendered HTML. Dynamic pages now use +JavaScript to update the UI in the browser by requesting server data as +JSON. Pyramid supports this with a *JSON renderer*. + +Background +========== + +As we saw in :doc:`templating`, view declarations can specify a +renderer. Output from the view is then run through the renderer, +which generates and returns the ``Response``. We first used a Chameleon +renderer, then a Jinja2 renderer. + +Renderers aren't limited, however, to templates that generate HTML. +Pyramid supplies a JSON renderer which takes Python data, +serializes it to JSON, and performs some other functions such as +setting the content type. In fact, you can write your own renderer (or +extend a built-in renderer) containing custom logic for your unique +application. + +Steps +===== + +#. First we copy the results of the ``view_classes`` step: + + .. code-block:: bash + + (env27)$ cd ..; cp -r view_classes json; cd json + (env27)$ python setup.py develop + +#. We add a new route for ``hello_json`` in + ``json/tutorial/__init__.py``: + + .. literalinclude:: json/tutorial/__init__.py + :linenos: + +#. Rather than implement a new view, we will "stack" another decorator + on the ``hello`` view: + + .. literalinclude:: json/tutorial/views.py + :linenos: + +#. We need a new functional test at the end of + ``json/tutorial/tests.py``: + + .. literalinclude:: json/tutorial/tests.py + :linenos: + +#. Run the tests: + + .. code-block:: bash + + (env27)$ nosetests tutorial + +#. Run your Pyramid application with: + + .. code-block:: bash + + (env27)$ pserve development.ini --reload + +#. Open ``http://localhost:6543/howdy.json`` in your browser and you + will see the resulting JSON response. + +Analysis +======== + +Earlier we changed our view functions and methods to return Python +data. This change to a data-oriented view layer made test writing +easier, decoupling the templating from the view logic. + +Since Pyramid has a JSON renderer as well as the templating renderers, +it is an easy step to return JSON. In this case we kept the exact same +view and arranged to return a JSON encoding of the view data. We did +this by: + +- Adding a route to map ``/howdy.json`` to a route name + +- Providing a ``@view_config`` that associated that route name with an + existing view + +- *overriding* the view defaults in the view config that mentions the + ``hello_json`` route, so that when the route is matched, we use the JSON + renderer rather than the ``home.pt`` template renderer that would otherwise + be used. + +In fact, for pure Ajax-style web applications, we could re-use the existing +route by using Pyramid's view predicates to match on the +``Accepts:`` header sent by modern Ajax implementation. + +Pyramid's JSON renderer uses the base Python JSON encoder, +thus inheriting its strengths and weaknesses. For example, +Python can't natively JSON encode DateTime objects. There are a number +of solutions for this in Pyramid, including extending the JSON renderer +with a custom renderer. + +.. seealso:: :ref:`pyramid:views_which_use_a_renderer`, + :ref:`pyramid:json_renderer`, and + :ref:`pyramid:adding_and_overriding_renderers` |
