Class ValueMapperFactoryRegistry
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object --+
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ValueMapperFactoryRegistry
An object clients can ask for functions fixing up values
for encoding.
A mapper factory is just a function that takes an AnnotatedColumn instance.
It must return either None (for "I don't know how to make a function for this
combination these column properties") or a callable that takes a value
of the given type and returns a mapped value.
To add a mapper, call registerFactory. To find a mapper for a
set of column properties, call getMapper -- column properties should
be an instance of AnnotatedColumn, but for now a dictionary with the
right keys should mostly do.
Mapper factories are tried in the reverse order of registration,
and the first that returns non-None wins, i.e., you should
register more general factories first. If no registred mapper declares
itself responsible, getMapper returns an identity function. If
you want to catch such a situation, you can use somthing like
res = vmfr.getMapper(...); if res is utils.identity ...
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__init__(self,
factories=None)
x.__init__(...) initializes x; see help(type(x)) for signature |
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getMapper(self,
colDesc)
returns a mapper for values with the python value instance,
according to colDesc. |
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Inherited from object:
__delattr__,
__format__,
__getattribute__,
__hash__,
__new__,
__reduce__,
__reduce_ex__,
__repr__,
__setattr__,
__sizeof__,
__str__,
__subclasshook__
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Inherited from object:
__class__
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__init__(self,
factories=None)
(Constructor)
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x.__init__(...) initializes x; see help(type(x)) for signature
- Overrides:
object.__init__
- (inherited documentation)
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returns a clone of the factory.
This is a copy, i.e., factories added will not change the original.
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returns the list of factories.
This is not a copy. It may be manipulated to remove or add
factories.
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returns a mapper for values with the python value instance,
according to colDesc.
This method may change colDesc.
We do a linear search here, so you shouldn't call this function too
frequently.
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