cache_lookup
Description:
Lookup attributes in the cache, or retrieve them from the object if necessary.
If this is a ObjectCache then this will lookup the attributes there first if available, otherwise will read them from the object and update the cache.
If this is not a ObjectCache, then the attributes will simply be read from the object.
This may block, use the asynchronous version when this is not desirable
Parameters:
| this |
the object |
| attr_types |
the types of attributes to update |
| cancellable |
optional cancellation object |
| n_attr_types |
the number of attribute types |
Returns:
|
the attributes retrieved or null on failure |