Source code for everest.representers.attributes

"""
Mapped resource attributes.

This file is part of the everest project. 
See LICENSE.txt for licensing, CONTRIBUTORS.txt for contributor information.

Created on June 8, 2011.
"""
from everest.representers.config import IGNORE_ON_READ_OPTION
from everest.representers.config import IGNORE_ON_WRITE_OPTION
from everest.representers.config import IGNORE_OPTION
from everest.representers.config import REPR_NAME_OPTION

__docformat__ = 'reStructuredText en'
__all__ = ['MappedAttribute',
           ]


class MappedAttribute(object):
    """
    Represents an attribute mapped from a class into a representation.

    Wraps a (read-only) resource attribute and mapping options which can be
    configured dynamically.
    """
    def __init__(self, attr, options=None):
        """
        :param attr: Resource attribute.
        """
        # Check given options.
        if options is None:
            options = {}
        # Make sure we have a valid representation name.
        if options.get(REPR_NAME_OPTION) is None:
            options[REPR_NAME_OPTION] = attr.name
        # Process the "ignore" option..
        do_ignore = options.get(IGNORE_OPTION)
        if not do_ignore is None:
            # The IGNORE option always overrides settings for IGNORE_ON_XXX.
            options[IGNORE_ON_READ_OPTION] = do_ignore
            options[IGNORE_ON_WRITE_OPTION] = do_ignore
        self.options = options
        #
        self.__attr = attr

    def clone(self, options=None):
        if options is None:
            options = {}
        new_options = self.options.copy()
        new_options.update(options)
        return MappedAttribute(self.__attr, options=new_options)

    @property
    def name(self):
        return self.__attr.name

    @property
    def kind(self):
        return self.__attr.kind

    @property
    def value_type(self):
        return self.__attr.value_type

    @property
    def entity_name(self):
        return self.__attr.entity_name

    @property
    def cardinality(self):
        return self.__attr.cardinality

    def __getattr__(self, attr_name):
        # Make options available as attributes.
        if attr_name in self.options:
            return self.options.get(attr_name)
        else:
            raise AttributeError(attr_name)

    def __str__(self):
        return '%s(%s -> %s, type %s)' % \
               (self.__class__.__name__, self.name, self.repr_name, self.kind)