api usecase to add a reference path to a metric objective

src/ifcopenshell-python/ifcopenshell/api/constraint/add_metric_reference.py

@@ -0,0 +1,45 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2021 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+import ifcopenshell
+
+class Usecase:
+    def __init__(self, file, metric=None, reference_path=None):
+        """
+        Adds a chain of references to a metric. The reference path is a string of the form "attribute.attribute.attribute" 
+        Used to reference a value of an attribute of an instance through a metric objective entity.
+        """
+        self.file = file
+        self.settings = {"metric": metric, "reference_path": reference_path}
+
+    def execute(self):
+        if self.settings["reference_path"]:
+            attributes = self.settings["reference_path"].split(".")
+            references_created = []
+            for i in range(len(attributes)):
+                if i == 0:
+                    reference = self.file.create_entity("IfcReference")
+                    reference.AttributeIdentifier = attributes[i]
+                    self.settings["metric"].ReferencePath = reference
+                    references_created.append(reference)
+                else:
+                    reference = self.file.create_entity("IfcReference")
+                    reference.AttributeIdentifier = attributes[i]
+                    references_created[i-1].InnerReference = reference
+                    references_created.append(reference)
+            return references_created