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Update docs about dataclass items and loaders

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Eugenio Lacuesta 2020-06-22 14:13:37 -03:00
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docs/topics/loaders.rst
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@ -84,9 +84,11 @@ Working with dataclass items
By default, :ref:`dataclass items <dataclass-items>` require all fields to be
passed when created. This could be an issue when using dataclass items with
item loaders, since fields could be populated incrementally.
item loaders: unless a pre-populated item is passed to the loader, fields
will be populated incrementally using the loader's :meth:`~ItemLoader.add_xpath`,
:meth:`~ItemLoader.add_css` and :meth:`~ItemLoader.add_value` methods.
Given the way that item loaders store data internally, the recommended approach
Given the way that item loaders store data internally, one approach
to overcome this is to define items using the :func:`~dataclasses.field`
function, with ``list`` as the ``default_factory`` argument::