def _property_facet ( self, getter, setter, validate, metadata ):
""" Returns a properly constructed 'property' facet.
"""
n = 0
if validate is not None:
n = _arg_count( validate )
facet = CFacet( 4 )
facet.property(
getter, _arg_count( getter ),
setter, _arg_count( setter ),
validate, n
)
facet.value_allowed( True )
facet.value_property( True )
facet.__dict__ = metadata
return facet
def Property ( fget = None, fset = None, fvalidate = None, force = False,
handler = None, facet = None, **metadata ):
""" Returns a facet whose value is a Python property.
Parameters
----------
fget : function
The "getter" function for the property
fset : function
The "setter" function for the property
fvalidate : function
The validation function for the property
force : Boolean
Indicates whether to use only the function definitions spedficied by
**fget** and **fset**, and not look elsewhere on the class.
handler : function
A facet handler function for the facet
facet : a facet definition or value that can be converted to a facet
A facet definition that constrains the values of the property facet
Description
-----------
If no getter or setter functions are specified (and **force** is not
True), it is assumed that they are defined elsewhere on the class whose
attribute this facet is assigned to. For example::
class Bar(HasFacets):
foo = Property(Float)
# Shadow facet attribute
_foo = Float
def _set_foo(self,x):
self._foo = x
def _get_foo(self):
return self._foo
You can use the **depends_on** metadata attribute to indicate that the
property depends on the value of another facet. The value of
**depends_on** is an extended name specifier for facets that the
property depends on. The property will a facet change notification if
any of the facets specified by **depends_on** change. For example::
class Wheel ( Part ):
axle = Instanced( Axle )
position = Property( depends_on = 'axle.chassis.position' )
For details of the extended facet name syntax, refer to the
on_facet_set() method of the HasFacets class.
"""
metadata[ 'type' ] = 'property'
# If no parameters specified, must be a forward reference (if not forced):
if (not force) and (fset is None):
sum = ((fget is not None) +
(fvalidate is not None) +
(facet is not None))
if sum <= 1:
if sum == 0:
return ForwardProperty( metadata )
handler = None
if fget is not None:
facet = fget
if facet is not None:
facet = facet_cast( facet )
if facet is not None:
fvalidate = handler = facet.handler
if fvalidate is not None:
fvalidate = handler.validate
if (fvalidate is not None) or (facet is not None):
if 'editor' not in metadata:
if (facet is not None) and (facet.editor is not None):
metadata[ 'editor' ] = facet.editor
return ForwardProperty( metadata, fvalidate, handler )
if fget is None:
metadata[ 'transient' ] = True
if fset is None:
fget = _undefined_get
fset = _undefined_set
else:
fget = _write_only
elif fset is None:
fset = _read_only
metadata[ 'transient' ] = True
if facet is not None:
facet = facet_cast( facet )
handler = facet.handler
if (fvalidate is None) and (handler is not None):
fvalidate = handler.validate
if ('editor' not in metadata) and (facet.editor is not None):
metadata[ 'editor' ] = facet.editor
metadata.setdefault( 'depends_on', getattr( fget, 'depends_on', None ) )
if ((metadata.get( 'depends_on' ) is not None) and
getattr( fget, 'cached_property', False )):
metadata.setdefault( 'cached', True )
n = 0
facet = CFacet( 4 )
facet.__dict__ = metadata.copy()
if fvalidate is not None:
n = _arg_count( fvalidate )
facet.property( fget, _arg_count( fget ),
fset, _arg_count( fset ),
fvalidate, n )
facet.handler = handler
return facet
