$cache public property (available since version 2.0.3)
The cache used to improve RBAC performance. This can be one of the following: an application component ID (e.g. cache) a configuration array a yii\caching\Cache object When this is not set, it means caching is not enabled. Note that by enabling RBAC cache, all auth items, rules and auth item parent-child relationships will be cached and loaded into memory. This will improve the performance of RBAC permission check. However, it does requ