bim.assing_class - add description, add poll check for selected objs

also added description to pie menu entry

src/blenderbim/blenderbim/bim/module/model/pie.py

@@ -26,6 +26,7 @@ from blenderbim.bim.ifc import IfcStore
 class OpenPieClass(bpy.types.Operator):
     bl_idname = "bim.open_pie_class"
     bl_label = "Open Pie Class"
+    bl_description = "Assign the IFC Class to the selected objects"
 
     def execute(self, context):
         bpy.ops.wm.call_menu_pie(name="VIEW3D_MT_PIE_bim_class")

src/blenderbim/blenderbim/bim/module/root/operator.py

@@ -166,7 +166,7 @@ class AssignClass(bpy.types.Operator, tool.Ifc.Operator):
     bl_idname = "bim.assign_class"
     bl_label = "Assign IFC Class"
     bl_options = {"REGISTER", "UNDO"}
-    bl_description = "Assign the IFC Class to the selected object"
+    bl_description = "Assign the IFC Class to the selected objects"
     obj: bpy.props.StringProperty()
     ifc_class: bpy.props.StringProperty()
     predefined_type: bpy.props.StringProperty()
@@ -175,6 +175,13 @@ class AssignClass(bpy.types.Operator, tool.Ifc.Operator):
     should_add_representation: bpy.props.BoolProperty(default=True)
     ifc_representation_class: bpy.props.StringProperty()
 
+    @classmethod
+    def poll(cls, context):
+        if not context.active_object and not context.selected_objects:
+            cls.poll_message_set("No object selected.")
+            return False
+        return True
+
     def _execute(self, context):
         props = context.scene.BIMRootProperties
         objects = [bpy.data.objects.get(self.obj)] if self.obj else context.selected_objects or [context.active_object]