BaseApi.get_interface_manager() wraps the manager module/library in a ManagerWrapper...

[sfa.git] / sfa / util / api.py

diff --git a/sfa/util/api.py b/sfa/util/api.py
index d0aadbe..cda8c88 100644 (file)
--- a/sfa/util/api.py
+++ b/sfa/util/api.py
@@ -95,6 +95,27 @@ def import_deep(name):
         mod = getattr(mod, comp)
     return mod
 
+class ManagerWrapper:
+    """
+    This class acts as a wrapper around an SFA interface manager module, but
+    can be used with any python module. The purpose of this class is raise a 
+    SfaNotImplemented exception if the a someone attepmts to use an attribute 
+    (could be a callable) thats not available in the library by checking the
+    library using hasattr. This helps to communicate better errors messages 
+    to the users and developers in the event that a specifiec operation 
+    is not implemented by a libarary and will generally be more helpful than
+    the standard AttributeError         
+    """
+    def __init__(self, manager, interface):
+        self.manager = manager
+        self.interface = interface
+        
+    def __getattr__(self, method):
+        
+        if not hasattr(self.manager, method):
+            raise SfaNotImplemented(method, self.interface)
+        return getattr(self.manager, method)
+        
 class BaseAPI:
 
     cache = None
@@ -138,28 +159,31 @@ class BaseAPI:
         self.aggregates = Aggregates(self)
 
 
-    def get_manager(self, manager_base = 'sfa.managers'):
+    def get_interface_manager(self, manager_base = 'sfa.managers'):
         """
         Returns the appropriate manager module for this interface.
         Modules are usually found in sfa/managers/
         """
         
         if self.interface in ['registry']:
-            mgr_type = self.api.config.SFA_REGISTRY_TYPE
+            mgr_type = self.config.SFA_REGISTRY_TYPE
             manager_module = manager_base + ".registry_manager_%s" % mgr_type
         elif self.interface in ['aggregate']:
-            mgr_type = self.api.config.SFA_AGGREGATE_TYPE
+            mgr_type = self.config.SFA_AGGREGATE_TYPE
             manager_module = manager_base + ".aggregate_manager_%s" % mgr_type 
         elif self.interface in ['slicemgr', 'sm']:
-            mgr_type = self.api.config.SFA_SM_TYPE
+            mgr_type = self.config.SFA_SM_TYPE
             manager_module = manager_base + ".slice_manager_%s" % mgr_type
         elif self.interface in ['component', 'cm']:
-            mgr_type = self.api.config.SFA_CM_TYPE
+            mgr_type = self.config.SFA_CM_TYPE
             manager_module = manager_base + ".component_manager_%s" % mgr_type
         else:
             raise SfaAPIError("No manager for interface: %s" % self.interface)  
-        manager = __import__(manager_module, fromlist=[manager_base])   
- 
+        manager = __import__(manager_module, fromlist=[manager_base])
+        # this isnt necessary but will hlep to produce better error messages
+        # if someone tries to access an operation this manager doesn't implement  
+        manager = ManagerWrapper(manager, self.interface)
+
         return manager
 
     def callable(self, method):