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"""
..
>>> from djangorestframework.parsers import FormParser
>>> from djangorestframework.resource import Resource
>>> from djangorestframework.compat import RequestFactory
>>> from urllib import urlencode
>>> req = RequestFactory().get('/')
>>> some_resource = Resource()
>>> trash = some_resource.dispatch(req)# Some variables are set only when calling dispatch
Data flatening
----------------
Here is some example data, which would eventually be sent along with a post request :
>>> inpt = urlencode([
... ('key1', 'bla1'),
... ('key2', 'blo1'), ('key2', 'blo2'),
... ])
Default behaviour for :class:`parsers.FormParser`, is to return a single value for each parameter :
>>> FormParser(some_resource).parse(inpt) == {'key1': 'bla1', 'key2': 'blo1'}
True
However, you can customize this behaviour by subclassing :class:`parsers.FormParser`, and overriding :meth:`parsers.FormParser.is_a_list` :
>>> class MyFormParser(FormParser):
...
... def is_a_list(self, key, val_list):
... return len(val_list) > 1
This new parser only flattens the lists of parameters that contain a single value.
>>> MyFormParser(some_resource).parse(inpt) == {'key1': 'bla1', 'key2': ['blo1', 'blo2']}
True
Submitting an empty list
--------------------------
When submitting an empty select multiple, like this one ::
<select multiple="multiple" name="key2"></select>
The browsers usually strip the parameter completely. A hack to avoid this, and therefore being able to submit an empty select multiple, is to submit a value that tells the server that the list is empty ::
<select multiple="multiple" name="key2"><option value="_empty"></select>
:class:`parsers.FormParser` provides the server-side implementation for this hack. Considering the following posted data :
>>> inpt = urlencode([
... ('key1', 'blo1'), ('key1', '_empty'),
... ('key2', '_empty'),
... ])
:class:`parsers.FormParser` strips the values ``_empty`` from all the lists.
>>> MyFormParser(some_resource).parse(inpt) == {'key1': 'blo1'}
True
Oh ... but wait a second, the parameter ``key2`` isn't even supposed to be a list, so the parser just stripped it.
>>> class MyFormParser(FormParser):
...
... def is_a_list(self, key, val_list):
... return key == 'key2'
...
>>> MyFormParser(some_resource).parse(inpt) == {'key1': 'blo1', 'key2': []}
True
Better like that. Note also that you can configure something else than ``_empty`` for the empty value by setting :class:`parsers.FormParser.EMPTY_VALUE`.
"""
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