Merge pull request #1853 from astatt/fix_ext_plugin

Add _ext_module variable to base python classes

hoomd/md/constrain.py

@@ -37,12 +37,16 @@ class Constraint(Force):
         for `isinstance` or `issubclass` checks.
     """
 
+    # Module where the C++ class is defined. Reassign this when developing an
+    # external plugin.
+    _ext_module = _md
+
     def _attach_hook(self):
         """Create the c++ mirror class."""
         if isinstance(self._simulation.device, hoomd.device.CPU):
-            cpp_cls = getattr(_md, self._cpp_class_name)
+            cpp_cls = getattr(self._ext_module, self._cpp_class_name)
         else:
-            cpp_cls = getattr(_md, self._cpp_class_name + "GPU")
+            cpp_cls = getattr(self._ext_module, self._cpp_class_name + "GPU")
 
         self._cpp_obj = cpp_cls(self._simulation.state._cpp_sys_def)
 

hoomd/md/external/field.py

@@ -27,11 +27,15 @@ class Field(force.Force):
         for `isinstance` or `issubclass` checks.
     """
 
+    # Module where the C++ class is defined. Reassign this when developing an
+    # external plugin.
+    _ext_module = _md
+
     def _attach_hook(self):
         if isinstance(self._simulation.device, hoomd.device.CPU):
-            cls = getattr(_md, self._cpp_class_name)
+            cls = getattr(self._ext_module, self._cpp_class_name)
         else:
-            cls = getattr(_md, self._cpp_class_name + "GPU")
+            cls = getattr(self._ext_module, self._cpp_class_name + "GPU")
 
         self._cpp_obj = cls(self._simulation.state._cpp_sys_def)
 

hoomd/md/external/wall.py

@@ -180,15 +180,19 @@ class WallPotential(force.Force):
         potentials.
     """
 
+    # Module where the C++ class is defined. Reassign this when developing an
+    # external plugin.
+    _ext_module = _md
+
     def __init__(self, walls):
         self._walls = None
         self.walls = hoomd.wall._WallsMetaList(walls, _to_md_cpp_wall)
 
     def _attach_hook(self):
         if isinstance(self._simulation.device, hoomd.device.CPU):
-            cls = getattr(_md, self._cpp_class_name)
+            cls = getattr(self._ext_module, self._cpp_class_name)
         else:
-            cls = getattr(_md, self._cpp_class_name + "GPU")
+            cls = getattr(self._ext_module, self._cpp_class_name + "GPU")
         self._cpp_obj = cls(self._simulation.state._cpp_sys_def)
         self._walls._sync({
             hoomd.wall.Sphere: