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======= ==============================
SEP 5
Title ItemBuilder API
Author Ismael Carnales, Pablo Hoffman
Created 2009-07-24
Status Obsoleted by :doc:`sep-008`
======= ==============================
=========================================
SEP-005: Detailed ``ItemBuilder`` API use
=========================================
Item class for examples:
.. code-block:: python
#!python
class NewsItem(Item):
url = fields.TextField()
headline = fields.TextField()
content = fields.TextField()
published = fields.DateField()
gSetting expanders
==================
.. code-block:: python
#!python
class NewsItemBuilder(ItemBuilder):
item_class = NewsItem
headline = reducers.Reducer(extract, remove_tags(), unquote(), strip)
This approach will override the Reducer class for ``BuilderFields`` depending
on their Item Field class:
* ``MultivaluedField`` = ``PassValue``
* ``TextField`` = ``JoinStrings``
* other = ``TakeFirst``
gSetting reducers
=================
.. code-block:: python
#!python
class NewsItemBuilder(ItemBuilder):
item_class = NewsItem
headline = reducers.TakeFirst(extract, remove_tags(), unquote(), strip)
published = reducers.Reducer(extract, remove_tags(), unquote(), strip)
As with the previous example this would select join_strings as the reducer for
content
gSetting expanders/reducers new way
===================================
.. code-block:: python
#!python
class NewsItemBuilder(ItemBuilder):
item_class = NewsItem
headline = BuilderField(extract, remove_tags(), unquote(), strip)
content = BuilderField(extract, remove_tags(), unquote(), strip)
class Reducer:
headline = TakeFirst
gExtending ``ItemBuilder``
==========================
.. code-block:: python
#!python
class SiteNewsItemBuilder(NewsItemBuilder):
published = reducers.Reducer(
extract, remove_tags(), unquote(), strip, to_date("%d.%m.%Y")
)
gExtending ``ItemBuilder`` using statich methods
================================================
.. code-block:: python
#!python
class SiteNewsItemBuilder(NewsItemBuilder):
published = reducers.Reducer(NewsItemBuilder.published, to_date("%d.%m.%Y"))
gUsing default_builder
======================
.. code-block:: python
#!python
class DefaultedNewsItemBuilder(ItemBuilder):
item_class = NewsItem
default_builder = reducers.Reducer(extract, remove_tags(), unquote(), strip)
This will use default_builder as the builder for every field in the item class.
As a reducer is not set reducers will be set based on Item Field classes.
gReset default_builder for a field
==================================
.. code-block:: python
#!python
class DefaultedNewsItemBuilder(ItemBuilder):
item_class = NewsItem
default_builder = reducers.Reducer(extract, remove_tags(), unquote(), strip)
url = BuilderField()
gExtending default ``ItemBuilder``
==================================
.. code-block:: python
#!python
class SiteNewsItemBuilder(NewsItemBuilder):
published = reducers.Reducer(
extract, remove_tags(), unquote(), strip, to_date("%d.%m.%Y")
)
gExtending default ``ItemBuilder`` using static methods
=======================================================
.. code-block:: python
#!python
class SiteNewsItemBuilder(NewsItemBuilder):
published = reducers.Reducer(NewsItemBuilder.default_builder, to_date("%d.%m.%Y"))
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