common: implement config_property descriptor tool

bliss/common/utils.py

@@ -160,3 +160,43 @@ def set_custom_members(src_obj, target_obj, pre_call=None):
         except AttributeError:
             pass
 
+
+class config_property(object):
+    """
+    Config descriptor to allow easy access to static configuration options
+
+    Only works on classes which have a `config` member that has `get()` and
+    `set()` methods (for example:
+    :class:`~bliss.config.motors.beacon_backend.StaticConfig`).
+
+    Example::
+
+        from bliss.comm.tcp import Tcp
+        from bliss.common.utils import config_property
+        from bliss.controllers.motor import Controller
+
+
+        class MyMotorController(Controller):
+
+            host_name = config_property('host')
+            port = config_property('port', converter=int, default=5000)
+
+            def initialize(self):
+                url = '{0}:{1}'.format(self.host_name, self.port)
+                self.tcp = Tcp(url=url)
+    """
+
+    def __init__(self, name, converter=str, default=None):
+        self.__name = name
+        self.__converter = converter
+        self.__default = default
+
+    def __get__(self, obj, objtype):
+        if obj is None:
+            return self
+        return obj.config.get(self.__name, converter=self.__converter,
+                              default=self.__default)
+
+    def __set__(self, obj, value):
+        obj.config.set(self.__name, value)
+

bliss/controllers/motors/mockup.py

@@ -16,6 +16,7 @@ from bliss.common import event
 
 from bliss.common.utils import object_method
 from bliss.common.utils import object_attribute_get, object_attribute_set
+from bliss.common.utils import config_property
 
 
 """
@@ -46,6 +47,9 @@ config_xml = """
 
 
 class Mockup(Controller):
+
+    host = config_property('host')
+
     def __init__(self, name, config, axes, encoders):
         Controller.__init__(self, name, config, axes, encoders)
 
@@ -64,8 +68,8 @@ class Mockup(Controller):
 
         # Access to the config.
         try:
-            self.host = self.config.get("host")
-        except:
+            self.host
+        except KeyError:
             elog.debug("no 'host' defined in config for %s" % name)
 
         # Adds Mockup-specific settings.