Class t.w.d.r.DAVPropertyMixIn(MetaDataMixin):

Part of twisted.web2.dav.resource View Source View In Hierarchy

Mix-in class which implements the DAV property access API in
L{IDAVResource}.

There are three categories of DAV properties, for the purposes of how this
class manages them.  A X{property} is either a X{live property} or a
X{dead property}, and live properties are split into two categories:

1. Dead properties.  There are properties that the server simply stores as
   opaque data.  These are store in the X{dead property store}, which is
   provided by subclasses via the L{deadProperties} method.

2. Live properties which are always computed.  These properties aren't
   stored anywhere (by this class) but instead are derived from the resource
   state or from data that is persisted elsewhere.  These are listed in the
   L{liveProperties} attribute and are handled explicitly by the
   L{readProperty} method.

3. Live properties may be acted on specially and are stored in the X{dead
   property store}.  These are not listed in the L{liveProperties} attribute,
   but may be handled specially by the property access methods.  For
   example, L{writeProperty} might validate the data and refuse to write
   data it deems inappropriate for a given property.

There are two sets of property access methods.  The first group
(L{hasProperty}, etc.) provides access to all properties.  They
automatically figure out which category a property falls into and act
accordingly.

The second group (L{hasDeadProperty}, etc.) accesses the dead property store
directly and bypasses any live property logic that exists in the first group
of methods.  These methods are used by the first group of methods, and there
are cases where they may be needed by other methods.  I{Accessing dead
properties directly should be done with caution.}  Bypassing the live
property logic means that values may not be the correct ones for use in
DAV requests such as PROPFIND, and may be bypassing security checks.  In
general, one should never bypass the live property logic as part of a client
request for property data.

Properties in the L{twisted_private_namespace} namespace are internal to the
server and should not be exposed to clients.  They can only be accessed via
the dead property store.