def get_by(self, field_name, field_value, cache_timeout=None):
"""A convienence function for looking up an object by a particular field
If the object is in the cache, returned the cached version.
If the object is not in the cache, do a basic .get() call and store it in the cache.
Fields used for lookup will be stored in the special cache, '__cached_field_names__'
so they can be automatically purged on the object's flush_cache() method
"""
if cache_timeout is None:
cache_timeout = getattr(settings, 'CACHE_TIMEOUT', 900)
# cache the field name that was used so flush_cache can purge them automatically
key = self.model.cache_key("__cached_field_names__")
cached_field_names = cache.get(key)
if cached_field_names is None:
cached_field_names = set()
cached_field_names.add(field_name)
cache.set(key, cached_field_names, cache_timeout)
key = self.model.cache_key("by_" + field_name, field_value)
obj = cache.get(key)
if obj is None:
obj = self.get(**{field_name: field_value})
cache.set(key_function_memcache_compat(key), obj, cache_timeout)
return obj
def cache_key(cls, *args):
"""
Generates a cache key from the object's class.__name__ and the arguments given
"""
vals = [cls.__name__] + [key_function_memcache_compat(arg) for arg in args]
return '_'.join(vals)
