You can now add and edit context dependent units including dimensional exponents

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

@@ -9,6 +9,7 @@ classes = (
     operator.RemoveUnit,
     operator.AddMonetaryUnit,
     operator.AddSIUnit,
+    operator.AddContextDependentUnit,
     operator.EnableEditingUnit,
     operator.DisableEditingUnit,
     operator.EditUnit,

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

@@ -1,4 +1,5 @@
 import bpy
+import json
 import ifcopenshell.api
 import ifcopenshell.util.unit
 import blenderbim.bim.helper
@@ -174,7 +175,7 @@ class AddSIUnit(bpy.types.Operator):
     def _execute(self, context):
         props = context.scene.BIMUnitProperties
         self.file = IfcStore.get_file()
-        unit = ifcopenshell.api.run(
+        ifcopenshell.api.run(
             "unit.add_si_unit",
             self.file,
             unit_type=props.named_unit_types,
@@ -185,6 +186,26 @@ class AddSIUnit(bpy.types.Operator):
         return {"FINISHED"}
 
 
+class AddContextDependentUnit(bpy.types.Operator):
+    bl_idname = "bim.add_context_dependent_unit"
+    bl_label = "Add Context Dependent Unit"
+    bl_options = {"REGISTER", "UNDO"}
+
+    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.add_context_dependent_unit", self.file, unit_type=props.named_unit_types, name="THINGAMAJIG"
+        )
+        Data.load(self.file)
+        bpy.ops.bim.load_units()
+        return {"FINISHED"}
+
+
+
 class EnableEditingUnit(bpy.types.Operator):
     bl_idname = "bim.enable_editing_unit"
     bl_label = "Enable Editing Unit"
@@ -195,13 +216,21 @@ class EnableEditingUnit(bpy.types.Operator):
         props = context.scene.BIMUnitProperties
         while len(props.unit_attributes) > 0:
             props.unit_attributes.remove(0)
-
         data = Data.units[self.unit]
-
-        blenderbim.bim.helper.import_attributes(data["type"], props.unit_attributes, data)
+        blenderbim.bim.helper.import_attributes(data["type"], props.unit_attributes, data, self.import_attributes)
         props.active_unit_id = self.unit
         return {"FINISHED"}
 
+    def import_attributes(self, name, prop, data):
+        if name == "Dimensions":
+            new = bpy.context.scene.BIMUnitProperties.unit_attributes.add()
+            new.name = name
+            new.is_null = data[name] is None
+            new.is_optional = False
+            new.data_type = "string"
+            new.string_value = json.dumps([e for e in IfcStore.get_file().by_id(data["id"]).Dimensions])
+            return True
+
 
 class DisableEditingUnit(bpy.types.Operator):
     bl_idname = "bim.disable_editing_unit"
@@ -223,7 +252,7 @@ class EditUnit(bpy.types.Operator):
 
     def _execute(self, context):
         props = context.scene.BIMUnitProperties
-        attributes = blenderbim.bim.helper.export_attributes(props.unit_attributes)
+        attributes = blenderbim.bim.helper.export_attributes(props.unit_attributes, self.export_attributes)
         self.file = IfcStore.get_file()
         unit = self.file.by_id(props.active_unit_id)
         if unit.is_a("IfcMonetaryUnit"):
@@ -235,3 +264,11 @@ class EditUnit(bpy.types.Operator):
         Data.load(IfcStore.get_file())
         bpy.ops.bim.load_units()
         return {"FINISHED"}
+
+    def export_attributes(self, attributes, prop):
+        if prop.name == "Dimensions":
+            try:
+                attributes[prop.name] = json.loads(prop.get_value())
+            except:
+                attributes[prop.name] = (0, 0, 0, 0, 0, 0, 0)
+            return True

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

@@ -43,8 +43,9 @@ class BIM_PT_units(Panel):
         elif self.props.unit_classes == "IfcSIUnit":
             row.prop(self.props, "named_unit_types", text="")
             row.operator("bim.add_si_unit", text="", icon="ADD")
-        else:
+        elif self.props.unit_classes == "IfcContextDependentUnit":
             row.prop(self.props, "named_unit_types", text="")
+            row.operator("bim.add_context_dependent_unit", text="", icon="ADD")
 
         self.layout.template_list(
             "BIM_UL_units",

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

@@ -0,0 +1,14 @@
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"unit_type": "USERDEFINED", "name": "THINGAMAJIG", "dimensions": (0, 0, 0, 0, 0, 0, 0)}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        return self.file.create_entity(
+            "IfcContextDependentUnit",
+            Dimensions=self.file.createIfcDimensionalExponents(*self.settings["dimensions"]),
+            UnitType=self.settings["unit_type"],
+            Name=self.settings["name"],
+        )

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

@@ -7,4 +7,12 @@ class Usecase:
 
     def execute(self):
         for name, value in self.settings["attributes"].items():
+            if name == "Dimensions":
+                dimensions = self.settings["unit"].Dimensions
+                if len(self.file.get_inverse(dimensions)) > 1:
+                    self.settings["unit"].Dimensions = self.file.createIfcDimensionalExponents(*value)
+                else:
+                    for i, exponent in enumerate(value):
+                        dimensions[i] = exponent
+                continue
             setattr(self.settings["unit"], name, value)

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

@@ -1,3 +1,4 @@
+import ifcopenshell.util.unit
 import ifcopenshell.util.element
 
 
@@ -9,10 +10,12 @@ class Usecase():
             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
+        unit_assignment = ifcopenshell.util.unit.get_unit_assignment(self.file)
+        if unit_assignment and self.settings["unit"] in unit_assignment.Units:
+            units = list(unit_assignment.Units)
+            units.remove(self.settings["unit"])
+            if units:
+                unit_assignment.Units = units
+            else:
+                self.file.remove(unit_assignment)
         ifcopenshell.util.element.remove_deep(self.file, self.settings["unit"])