フックポイント¶

マッピング処理の途中で何か追加の処理を行いたい場合、いくつかのフックポイントを使用できます。

Mapper.filter_FOO¶

フィールドの値変換の前に実行されます。FOOはフィールド名に置き換えてください。

NonKeyField を使った場合、ここでマッピングに利用する値を生成することができます。

>>> from bpmappers import Mapper, NonKeyField
>>> class MyMapper(Mapper):
...     value = NonKeyField()
...     def filter_value(self):
...         return 10
...
>>> mapper = MyMapper()
>>> mapper.as_dict()
OrderedDict([('value', 10)])

Mapper.after_filter_FOO¶

フィールドの値変換の後に実行されます。FOOはフィールド名に置き換えてください。第一引数に、filter_FOOの結果の値が入ります。

>>> from bpmappers import Mapper, NonKeyField
>>> class MyMapper(Mapper):
...     value = NonKeyField()
...     def filter_value(self):
...         return "oyoyo"
...
...     def after_filter_value(self, val):
...         return val.capitalize()
...
>>> mapper = MyMapper()
>>> print(mapper.as_dict())
OrderedDict([('value', 'Oyoyo')])

Mapper.attach_FOO¶

マッピングの結果の辞書に値を追加する代わりに実行されます。値を追加しない場合や、値の追加位置を変更する場合などに使用できます。

>>> from bpmappers import Mapper, NonKeyField, RawField
>>> class Point(object):
...     def __init__(self, x, y):
...         self.x = x
...         self.y = y
...
>>> class PointMapper(Mapper):
...     x = RawField("x")
...     y = RawField("y")
...
...     def attach_x(self, parsed, v):
...         parsed[v] = (v, v*v, v*v*v, v*v*v*v)
...
...     def attach_y(self, parsed, v):
...         parsed[v] = "y is %s" % v
...
>>> mapper = PointMapper(Point(10, 20))
>>> print(mapper.as_dict())
OrderedDict([(10, (10, 100, 1000, 10000)), (20, 'y is 20')])

Field.callback¶

フィールドの値変換の前に実行されます。 filter_FOO の後にフィールドクラスで実行されます。

>>> from bpmappers import Mapper, RawField, DelegateField
>>> class Person(object):
...     def __init__(self, name):
...        self.name = name
...
>>> class PersonInfoMapper(Mapper):
...     info = RawField("name", callback = lambda v : "name:%s" % v)
...
>>>
>>> class PersonInfoMapper2(Mapper):
...     info = RawField("name", callback = lambda v : "name:%s" % v)
...
...     def filter_info(self, v):
...         return v+v
...
>>> mapper = PersonInfoMapper(Person("bucho"))
>>> print(mapper.as_dict())
OrderedDict([('info', 'name:bucho')])
>>> mapper = PersonInfoMapper2(Person("bucho"))
>>> print(mapper.as_dict())
OrderedDict([('info', 'name:buchobucho')])

Field.after_callback¶

フィールドの値変換の後に実行されます。 after_filter_FOO の前にフィールドクラスで実行されます。

>>> from bpmappers import Mapper, RawField, ListDelegateField
>>> class Person(object):
...     def __init__(self, name):
...         self.name = name
...
>>> class Book(object):
...     def __init__(self, title, authors):
...         self.title = title
...         self.authors = authors
...
>>> class AuthorMapper(Mapper):
...     author = RawField("name")
...
>>> class BookMapper(Mapper):
...     title = RawField()
...     authors = ListDelegateField(AuthorMapper)
...
>>> book = Book("be clound", [Person("bucho"), Person("shacho")])
>>> print(BookMapper(book).as_dict())
OrderedDict([('title', 'be clound'), ('authors', [OrderedDict([('author', 'bucho')]), OrderedDict([('author', 'shacho')])])])
>>> def get_vals(items):
...     """
...     辞書のリストから、値だけを取り出す関数
...
...     >>> get_vals([{"pt":1}, {"pt":2}])
...     [1, 2]
...     """
...     result = []
...     for dic in items:
...         for k, v in dic.items():
...             result.append(v)
...     return result
...
>>> class BookMapperExt(Mapper):
...     title = RawField()
...     authors = ListDelegateField(AuthorMapper, after_callback=get_vals)
...
>>> book = Book("be clound", [Person("bucho"), Person("shacho")])
>>> print(BookMapperExt(book).as_dict())
OrderedDict([('title', 'be clound'), ('authors', ['bucho', 'shacho'])])

注釈

filter_FOO, after_filter_FOO, callback, after_callbackは以下の順序で呼ばれます。

filter_FOO
callback
after_callback
after_filter_FOO

実行例

>>> from bpmappers import Mapper, RawField, DelegateField
>>> class Person(object):
...     def __init__(self, name):
...         self.name = name
...
>>> class PersonInfoMapper(Mapper):
...     info = RawField("name",
...                     callback= lambda v :  "( cb: %s )" % v,
...                     after_callback = lambda v :  "[ after_cb: %s ]" % v)
...
...     def filter_info(self, v):
...         return "< filter: %s >" % v
...
...     def after_filter_info(self, v):
...         return "{ after_filter: %s }" % v
...
>>> mapper = PersonInfoMapper(Person("BP"))
>>> print(mapper.as_dict())
OrderedDict([('info', '{ after_filter: [ after_cb: ( cb: < filter: BP > ) ] }')])

Mapper.key_name¶

キー名を変更したい場合などに使用します。

>>> from bpmappers import Mapper, RawField
>>> class NameSpaceMapper(Mapper):
...     name = RawField()
...     def key_name(self, name,  value, field):
...         return 'namespace:%s' % name
...
>>> NameSpaceMapper(dict(name='bucho')).as_dict()
OrderedDict([('namespace:name', 'bucho')])