Resolve L2SS-449 "Add deviceproxy to devices"

Closes L2SS-449

tangostationcontrol/tangostationcontrol/devices/lofar_device.py

@@ -15,7 +15,7 @@ from abc import abstractmethod
 
 # PyTango imports
 from tango.server import Device, command, DeviceMeta, attribute
-from tango import AttrWriteType, DevState, DebugIt, Attribute, DeviceProxy
+from tango import AttrWriteType, DevState, DebugIt, Attribute, DeviceProxy, DevFailed
 
 import time
 import math
@@ -86,6 +86,15 @@ class lofar_device(Device, metaclass=AbstractDeviceMetas):
 
         self.set_state(DevState.OFF)
 
+        # register a proxy to ourselves, to interact with
+        # our attributes and commands as a client would.
+        #
+        # this is required to get/set attributes.
+        #
+        # we cannot write directly to our attribute, as that would not
+        # trigger a write_{name} call. See https://www.tango-controls.org/community/forum/c/development/c/accessing-own-deviceproxy-class/?page=1#post-2021
+        self.proxy = DeviceProxy(self.get_name())
+
     @log_exceptions()
     def delete_device(self):
         """Hook to delete resources allocated in init_device.
@@ -221,12 +230,6 @@ class lofar_device(Device, metaclass=AbstractDeviceMetas):
                 2) Any remaining default properties are set.
         """
 
-        # we cannot write directly to our attribute, as that would not
-        # trigger a write_{name} call. See https://www.tango-controls.org/community/forum/c/development/c/accessing-own-deviceproxy-class/?page=1#post-2021
-
-        # obtain a proxy to myself, to write values
-        proxy = DeviceProxy(self.get_name())
-
         # collect all attributes for which defaults are provided
         attributes_with_defaults = [name for name in dir(self)
                                     # collect all attribute members
@@ -244,7 +247,7 @@ class lofar_device(Device, metaclass=AbstractDeviceMetas):
 
                 # set the attribute to the configured default
                 self.debug_stream(f"Setting attribute {name} to {default_value}")
-                proxy.write_attribute(name, default_value)
+                self.proxy.write_attribute(name, default_value)
             except Exception as e:
                 # log which attribute we're addressing
                 raise Exception(f"Cannot assign default to attribute {name}") from e
@@ -271,13 +274,11 @@ class lofar_device(Device, metaclass=AbstractDeviceMetas):
             pollperiod:  how often to check the attribute, in seconds.
         """
 
-        attr = getattr(self, attr_name)
-
         # Poll every half a second
         for _ in range(math.ceil(timeout/pollperiod)):
-            if attr != value:
+            if getattr(self.proxy, attr_name) != value:
                 return
 
             time.sleep(pollperiod)
 
-        raise Exception(f"{attr} != {value} after f{timeout} seconds still.")
+        raise Exception(f"{attr_name} != {value} after {timeout} seconds still.")