You can now add and edit monetary units, and basic editing of other unit types.

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

@@ -0,0 +1,9 @@
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"currency": "DOLLARYDOO"}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        return self.file.create_entity("IfcMonetaryUnit", self.settings["currency"])

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

@@ -1,44 +1,55 @@
+import ifcopenshell
 import ifcopenshell.util.unit
 
 
-class Usecase():
+class Usecase:
     def __init__(self, file, **settings):
         self.file = file
         self.settings = {
-            "length": {
-                "is_metric": True,
-                "raw": "MILLIMETERS"
-            },
-            "area": {
-                "is_metric": True,
-                "raw": "METERS"
-            },
-            "volume": {
-                "is_metric": True,
-                "raw": "METERS"
-            },
+            "units": None,
+            "length": {"is_metric": True, "raw": "MILLIMETERS"},
+            "area": {"is_metric": True, "raw": "METERS"},
+            "volume": {"is_metric": True, "raw": "METERS"},
         }
         for key, value in settings.items():
             self.settings[key] = value
 
     def execute(self):
-        for unit_type, data in self.settings.items():
-            if data["is_metric"]:
-                data["ifc"] = self.create_metric_unit(unit_type, data)
-            else:
-                data["ifc"] = self.create_imperial_unit(unit_type, data)
+        # We're going to refactor this to split unit creation and assignment
+        if self.settings["units"]:
+            units = self.settings["units"]
+        else:
+            del self.settings["units"]  # TODO refactor
+            units = []
+            for unit_type, data in self.settings.items():
+                if data["is_metric"]:
+                    units.append(self.create_metric_unit(unit_type, data))
+                else:
+                    units.append(self.create_imperial_unit(unit_type, data))
+
+        unit_assignment = self.get_unit_assignment()
+        self.assign_units(unit_assignment, units)
+        return unit_assignment
+
+    def get_unit_assignment(self):
         unit_assignment = self.file.by_type("IfcUnitAssignment")
         if unit_assignment:
             unit_assignment = unit_assignment[0]
             # TODO: handle unit rewriting, which is complicated
         else:
-            unit_assignment = self.file.createIfcUnitAssignment([u["ifc"] for u in self.settings.values()])
+            unit_assignment = self.file.createIfcUnitAssignment()
             if self.file.schema == "IFC2X3":
                 self.file.by_type("IfcProject")[0].UnitsInContext = unit_assignment
             else:
                 self.file.by_type("IfcContext")[0].UnitsInContext = unit_assignment
         return unit_assignment
 
+    def assign_units(self, unit_assignment, new_units):
+        units = set(unit_assignment.Units or [])
+        for unit in new_units:
+            units.add(unit)
+        unit_assignment.Units = list(units)
+
     def create_metric_unit(self, unit_type, data):
         type_prefix = ""
         if unit_type == "area":
@@ -72,7 +83,9 @@ class Usecase():
             name = "{}inch".format(name_prefix + " " if name_prefix else "")
         elif data["raw"] == "FEET":
             name = "{}foot".format(name_prefix + " " if name_prefix else "")
-        value_component = self.file.create_entity("IfcReal", **{"wrappedValue": ifcopenshell.util.unit.si_conversions[name]})
+        value_component = self.file.create_entity(
+            "IfcReal", **{"wrappedValue": ifcopenshell.util.unit.si_conversions[name]}
+        )
         conversion_factor = self.file.createIfcMeasureWithUnit(value_component, si_unit)
         return self.file.createIfcConversionBasedUnit(
             dimensional_exponents, "{}UNIT".format(unit_type.upper()), name, conversion_factor

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

@@ -0,0 +1,10 @@
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"unit": None, "attributes": {}}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        for name, value in self.settings["attributes"].items():
+            setattr(self.settings["unit"], name, value)

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

@@ -0,0 +1,10 @@
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"unit": None, "attributes": {}}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        for name, value in self.settings["attributes"].items():
+            setattr(self.settings["unit"], name, value)

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

@@ -0,0 +1,10 @@
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"unit": None, "attributes": {}}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        for name, value in self.settings["attributes"].items():
+            setattr(self.settings["unit"], name, value)