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- NamedValueAccess
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- NamedValueAccessWrapper
- exceptions.LookupError(exceptions.StandardError)
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- NamedValueAccessError
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- ValueForKeyError
class NamedValueAccess |
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Mix-in class for accessing Python objects by named attributes.
This class is intended to be ancestor class such that you can say:
from NamedValueAccess import *
age = someObj.valueForName("age")
name = someObj.valueForName("info.fields.name")
This can be useful in setups where you wish to textually refer to the
objects in a program, such as an HTML template processed in the context
of an object-oriented framework.
Keys can be matched to either methods or instance variables and with
or without underscores.
valueForName() can also traverse bona fide dictionaries (DictType).
You can safely import * from this module.
Only the NamedValueAccess class is exported.
There is no __init__() method and never will be.
You'll see the terms 'key' and 'name' in the class and its documentation.
A 'key' is a single identifier such as 'foo'. A name could be key, or a
qualified key, such as 'foo.bar.boo'. Names are generally more convenient
and powerful, while key-oriented methods are more efficient and provide
the atomic functionality that name-oriented methods are built upon.
From a usage point of view, you normally just use the 'name' methods
and forget about the 'key'.
@@ 2000-05-21 ce: This class causes problems when used in WebKit for logging.
Perhaps circular references?
Involving self?
Having to do with methods bound to their objects?
@@ 2000-03-03 ce: document instance variables
@@ 2000-04-24 ce: Some classes like UserDict need to use getitem()
instead of getattr() and don't need to deal with _bindingForGetKey().
@@ 2000-05-31 ce: Rename this class to NamedValues, NamedValueAccess, ValuesByName
@@ This class probably needs to be in MiscUtils, as it's being used in that
way while MiddleKit was intended for "enterprise/business objects". |
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Methods defined here:
- handleUnknownSetKey(self, key)
- hasValueForKey(self, key)
- Check whether key is available.
Returns true if the key is available, although that does not guarantee
that there will not be errors caused by retrieving the key.
- hasValueForName(self, keysString)
- Check whether name is available.
- resetKeyBindings(self)
- Rest all key bindings, releasing alreaedy referenced values.
- setValueForKey(self, key, value)
- Set value for a given key.
Suppose key is 'foo'.
This method sets the value with the following precedence:
1. Public attributes before private attributes
2. Methods before non-methods
More specifically, this method then uses one of the following:
@@ 2000-03-04 ce: fill in
... or invokes handleUnknownSetKey().
- valueForKey(self, key, default=<class MiscUtils.NoDefault at 0x8c81d0>)
- Get value for given key.
Suppose key is 'foo'.
This method returns the value with the following precedence:
1. Methods before non-methods
2. Public attributes before private attributes
More specifically, this method then returns one of the following:
* foo()
* _foo()
* self.foo
* self._foo
... or default, if it was specified,
otherwise invokes and returns result of valueForUnknownKey().
Note that valueForUnknownKey() normally returns an exception.
See valueForName() which is a more advanced version of this method
that allows multiple, qualified keys.
- valueForKeySequence(self, listOfKeys, default=None)
- Get the value for the given list of keys.
- valueForName(self, keysString, default=None)
- Get the value for the given keysString.
This is the more advanced version of valueForKey(), which can only
handle single names. This method can handle
'foo', 'foo1.foo2', 'a.b.c.d', etc.
It will traverse dictionaries if needed.
- valueForUnknownKey(self, key, default)
- valuesForNames(self, keys, default=None, defaults=None, forgive=0, includeNames=0)
- Get all values for given names.
Returns a list of values that match the given keys, each of which is
passed through valueForName() and so could be of the form 'a.b.c'.
keys and defaults are sequences.
default is any kind of object.
forgive and includeNames are flags.
If default is not None, then it is substituted when a key is not found.
Otherwise, if defaults is not None, then it's corresponding/parallel
value for the current key is substituted when a key is not found.
Otherwise, if forgive is true, then unknown keys simply don't produce
any values.
Otherwise, if default and defaults are None, and forgive is false,
then the unknown keys will probably raise an exception through
valueForUnknownKey() although that method can always return
a final, default value.
if keys is None, then None is returned.
If keys is an empty list, then None is returned.
Often these last four arguments are specified by key.
Examples:
names = ['origin.x', 'origin.y', 'size.width', 'size.height']
obj.valuesForNames(names)
obj.valuesForNames(names, default=0.0)
obj.valuesForNames(names, defaults=[0.0, 0.0, 100.0, 100.0])
obj.valuesForNames(names, forgive=0)
@@ 2000-03-04 ce: includeNames is only supported when forgive=1.
It should be supported for the other cases.
It should be documented.
It should be included in the test cases.
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class NamedValueAccessWrapper(NamedValueAccess) |
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Mix-in class for accessing Python objects by named attributes.
This provides a wrapper around an existing object which will respond
to the methods of NamedValueAccess. By using the wrapper, you can
stick with objects and methods such as obj.valueForName('x.y') (as
opposed to functions like valueForName()) and refrain from modifying
the existing class hierarchy with NamedValueAccess.
Example:
wrapper = NamedValueAccessWrapper(obj)
print wrapper.valueForName('manager.name') |
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Methods defined here:
- __init__(self, object)
- hasValueForKey(self, key)
- valueForKey(self, key, default=<class MiscUtils.NoDefault at 0x8c81d0>)
- valueForName(self, key, default=<class MiscUtils.NoDefault at 0x8c81d0>)
Methods inherited from NamedValueAccess:
- handleUnknownSetKey(self, key)
- hasValueForName(self, keysString)
- Check whether name is available.
- resetKeyBindings(self)
- Rest all key bindings, releasing alreaedy referenced values.
- setValueForKey(self, key, value)
- Set value for a given key.
Suppose key is 'foo'.
This method sets the value with the following precedence:
1. Public attributes before private attributes
2. Methods before non-methods
More specifically, this method then uses one of the following:
@@ 2000-03-04 ce: fill in
... or invokes handleUnknownSetKey().
- valueForKeySequence(self, listOfKeys, default=None)
- Get the value for the given list of keys.
- valueForUnknownKey(self, key, default)
- valuesForNames(self, keys, default=None, defaults=None, forgive=0, includeNames=0)
- Get all values for given names.
Returns a list of values that match the given keys, each of which is
passed through valueForName() and so could be of the form 'a.b.c'.
keys and defaults are sequences.
default is any kind of object.
forgive and includeNames are flags.
If default is not None, then it is substituted when a key is not found.
Otherwise, if defaults is not None, then it's corresponding/parallel
value for the current key is substituted when a key is not found.
Otherwise, if forgive is true, then unknown keys simply don't produce
any values.
Otherwise, if default and defaults are None, and forgive is false,
then the unknown keys will probably raise an exception through
valueForUnknownKey() although that method can always return
a final, default value.
if keys is None, then None is returned.
If keys is an empty list, then None is returned.
Often these last four arguments are specified by key.
Examples:
names = ['origin.x', 'origin.y', 'size.width', 'size.height']
obj.valuesForNames(names)
obj.valuesForNames(names, default=0.0)
obj.valuesForNames(names, defaults=[0.0, 0.0, 100.0, 100.0])
obj.valuesForNames(names, forgive=0)
@@ 2000-03-04 ce: includeNames is only supported when forgive=1.
It should be supported for the other cases.
It should be documented.
It should be included in the test cases.
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