source: TI12-security/trunk/NDG_XACML/ndg/xacml/core/attributevalue.py @ 6792

"""NDG XACML attribute type definition

NERC DataGrid Project
"""
__author__ = "P J Kershaw"
__date__ = "25/02/10"
__copyright__ = "(C) 2010 Science and Technology Facilities Council"
__contact__ = "Philip.Kershaw@stfc.ac.uk"
__license__ = "BSD - see LICENSE file in top-level directory"
__contact__ = "Philip.Kershaw@stfc.ac.uk"
__revision__ = "$Id: $"
from ndg.xacml.core.expression import Expression
    

class AttributeValue(Expression):
    """XACML Attribute Value type"""
    ELEMENT_LOCAL_NAME = 'AttributeValue'
    __slots__ = ('__value',) 
    
    def __init__(self):
        super(AttributeValue, self).__init__()
        self.__value = None
           
    def _get_value(self):
        return self.__value

    def _set_value(self, value):
        if not isinstance(value, basestring):
            raise TypeError('Expecting %r type for "value" '
                            'attribute; got %r' % (basestring, type(value)))
            
        self.__value = value  

    value = property(_get_value, _set_value, None, "expression value") 
    
    def evaluate(self, context):
        """Evaluate the result of the expression in a condition
        @param context: the request context
        @type context: ndg.xacml.core.context.request.Request
        @return: attribute value(s) resulting from execution of this expression
        in a condition
        @rtype: AttributeValue/NoneType  
        """ 
        return self.__value