You can now delete unit assignments

src/blenderbim/blenderbim/bim/module/unit/__init__.py

@@ -4,6 +4,8 @@ from . import ui, prop, operator
 classes = (
     operator.AssignUnit,
     operator.LoadUnits,
+    operator.DisableUnitEditingUI,
+    operator.RemoveUnit,
     prop.Unit,
     prop.BIMUnitProperties,
     ui.BIM_PT_units,

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

@@ -88,3 +88,31 @@ class LoadUnits(bpy.types.Operator):
         props.is_editing = True
         # bpy.ops.bim.disable_editing_unit()
         return {"FINISHED"}
+
+
+class DisableUnitEditingUI(bpy.types.Operator):
+    bl_idname = "bim.disable_unit_editing_ui"
+    bl_label = "Disable Unit Editing UI"
+    bl_options = {"REGISTER", "UNDO"}
+
+    def execute(self, context):
+        context.scene.BIMUnitProperties.is_editing = False
+        return {"FINISHED"}
+
+
+class RemoveUnit(bpy.types.Operator):
+    bl_idname = "bim.remove_unit"
+    bl_label = "Remove Unit"
+    bl_options = {"REGISTER", "UNDO"}
+    unit: bpy.props.IntProperty()
+
+    def execute(self, context):
+        return IfcStore.execute_ifc_operator(self, context)
+
+    def _execute(self, context):
+        props = context.scene.BIMUnitProperties
+        self.file = IfcStore.get_file()
+        ifcopenshell.api.run("unit.remove_unit", self.file, **{"unit": self.file.by_id(self.unit)})
+        Data.load(self.file)
+        bpy.ops.bim.load_units()
+        return {"FINISHED"}

src/blenderbim/blenderbim/bim/module/unit/ui.py

@@ -26,8 +26,8 @@ class BIM_PT_units(Panel):
         row = self.layout.row(align=True)
         row.label(text="{} Units Found".format(len(Data.unit_assignment)), icon="SNAP_GRID")
         if self.props.is_editing:
-            row.operator("bim.add_group", text="", icon="ADD")
-            row.operator("bim.disable_group_editing_ui", text="", icon="CANCEL")
+            # row.operator("bim.add_unit", text="", icon="ADD")
+            row.operator("bim.disable_unit_editing_ui", text="", icon="CANCEL")
         else:
             row.operator("bim.load_units", text="", icon="GREASEPENCIL")
 
@@ -49,3 +49,4 @@ class BIM_UL_units(UIList):
             row = layout.row(align=True)
             row.label(text=item.unit_type or "No Type", icon=item.icon)
             row.label(text=item.name or "Unnamed")
+            row.operator("bim.remove_unit", text="", icon="X").unit = item.ifc_definition_id

src/ifcopenshell-python/ifcopenshell/api/unit/data.py

@@ -17,6 +17,8 @@ class Data:
         if not file:
             return
         cls.file = file
+        cls.unit_assignment = []
+        cls.units = {}
         unit_assignment = cls.file.by_type("IfcUnitAssignment")
         if not unit_assignment:
             return

src/ifcopenshell-python/ifcopenshell/api/unit/remove_unit.py

@@ -0,0 +1,18 @@
+import ifcopenshell.util.element
+
+
+class Usecase():
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"unit": None}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        unit_assignment = self.file.by_type("IfcUnitAssignment")[0]
+        units = list(unit_assignment.Units)
+        units.remove(self.settings["unit"])
+        if not units:
+            return
+        unit_assignment.Units = units
+        ifcopenshell.util.element.remove_deep(self.file, self.settings["unit"])