71 lines
2.5 KiB
ReStructuredText
71 lines
2.5 KiB
ReStructuredText
.. _jsonify:
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JSON Support
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============
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Pecan includes a simple, easy-to-use system for generating and serving
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``JSON``. To get started, create a file in your project called
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``json.py`` and import it in your project's ``app.py``.
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Your ``json`` module will contain a series of rules for generating
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``JSON`` from objects you return in your controller, utilizing
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"generic" function support from the
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`simplegeneric <http://pypi.python.org/pypi/simplegeneric>`_ library.
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Let's say that we have a controller in our Pecan application which
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we want to use to return ``JSON`` output for a ``User`` object::
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from myproject.lib import get_current_user
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class UsersController(object):
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@expose('json')
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def current_user(self):
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'''
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return an instance of myproject.model.User which represents
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the current authenticated user
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'''
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return get_current_user()
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In order for this controller to function, Pecan will need to know how to
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convert the ``User`` object into a ``JSON``-friendly data structure. One
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way to tell Pecan how to convert an object into ``JSON`` is to define a
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rule in your ``json.py``::
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from pecan.jsonify import jsonify
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from myproject import model
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@jsonify.when_type(model.User)
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def jsonify_user(user):
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return dict(
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name = user.name,
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email = user.email,
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birthday = user.birthday.isoformat()
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)
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In this example, when an instance of the ``model.User`` class is
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returned from a controller which is configured to return ``JSON``, the
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``jsonify_user`` rule will be called to generate that ``JSON``. Note
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that the rule does not generate a ``JSON`` string, but rather generates
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a Python dictionary which contains only ``JSON`` friendly data types.
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Alternatively, the rule can be specified on the object itself, by
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specifying a ``__json__`` method on the object::
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class User(object):
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def __init__(self, name, email, birthday):
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self.name = name
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self.email = email
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self.birthday = birthday
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def __json__(self):
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return dict(
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name = self.name,
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email = self.email,
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birthday = self.birthday.isoformat()
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)
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The benefit of using a ``json.py`` module is having all of your ``JSON``
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rules defined in a central location, but some projects prefer the
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simplicity of keeping the ``JSON`` rules attached directly to their
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model objects.
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