Base: [skip ci] add an enum for unit schemes in Python to avoid to work with numbers

src/App/FreeCADInit.py

@@ -824,6 +824,27 @@ App.Units.DynamicViscosity             = App.Units.Unit(-1,1,-1)
 App.Units.KinematicViscosity           = App.Units.Unit(2,0,-1)
 App.Units.VacuumPermittivity           = App.Units.Unit(-3,-1,4,2)
 
+# Add an enum for the different unit schemes
+if sys.version_info.major < 3:
+    IntEnum = object
+else:
+    from enum import IntEnum
+
+# The values must match with that of the
+# C++ enum class UnitSystem
+class Scheme(IntEnum):
+    SI1 = 0
+    SI2 = 1
+    Imperial1 = 2
+    ImperialDecimal = 3
+    Centimeters = 4
+    ImperialBuilding = 5
+    MmMin = 6
+    ImperialCivil = 7
+    FemMilliMeterNewton = 8
+
+App.Units.Scheme = Scheme
+
 # clean up namespace
 del(InitApplications)
 del(test_ascii)

src/Mod/Fem/femsolver/elmer/writer.py

@@ -108,7 +108,7 @@ class Writer(object):
         # the units are consistent
         # TODO retrieve the seven base units from FreeCAD unit schema
         # instead of hard coding them here for a second once
-        self.unit_schema = 0
+        self.unit_schema = Units.Scheme.SI1
         self.unit_system = {  # standard FreeCAD Base units = unit schema 0
             "L": "mm",
             "M": "kg",
@@ -119,13 +119,13 @@ class Writer(object):
             "J": "cd",
         }
         param = ParamGet("User parameter:BaseApp/Preferences/Units")
-        self.unit_schema = param.GetInt("UserSchema", 0)
-        if self.unit_schema == 0:
+        self.unit_schema = param.GetInt("UserSchema", Units.Scheme.SI1)
+        if self.unit_schema == Units.Scheme.SI1:
             Console.PrintMessage(
                 "The FreeCAD standard unit schema mm/kg/s is used. "
                 "Elmer sif-file writing is done in Standard FreeCAD units.\n"
             )
-        elif self.unit_schema == 1:
+        elif self.unit_schema == Units.Scheme.SI2:
             Console.PrintMessage(
                 "The SI unit schema m/kg/s is used. "
                 "Elmer sif-file writing is done in SI-units.\n"
@@ -139,7 +139,7 @@ class Writer(object):
                 "N": "mol",
                 "J": "cd",
             }
-        elif self.unit_schema == 8:
+        elif self.unit_schema == Units.Scheme.FemMilliMeterNewton:
             # see also unit comment in calculix writer
             Console.PrintMessage(
                 "The FEM unit schema mm/N/s is used. "
@@ -154,12 +154,12 @@ class Writer(object):
                 "N": "mol",
                 "J": "cd",
             }
-        elif self.unit_schema > 1 and self.unit_schema != 8:
+        elif self.unit_schema > Units.Scheme.SI2 and self.unit_schema != Units.Scheme.FemMilliMeterNewton:
             Console.PrintMessage(
                 "Unit schema: {} not supported by Elmer writer. "
                 "The FreeCAD standard unit schema mm/kg/s is used. "
                 "Elmer sif-file writing is done in Standard FreeCAD units.\n"
-                .format(self.unit_schema)
+                .format(Units.listSchemas(self.unit_schema))
             )
 
     def _getFromUi(self, value, unit, outputDim):
@@ -277,7 +277,7 @@ class Writer(object):
     def _handleSimulation(self):
         self._simulation("Coordinate System", "Cartesian 3D")
         self._simulation("Coordinate Mapping", (1, 2, 3))
-        if self.unit_schema == 1:
+        if self.unit_schema == Units.Scheme.SI2:
             self._simulation("Coordinate Scaling", 0.001)
             Console.PrintMessage(
                 "'Coordinate Scaling = Real 0.001' was inserted into the solver input file.\n"
@@ -881,7 +881,7 @@ class Writer(object):
         s["Procedure"] = sifio.FileAttr("ResultOutputSolve/ResultOutputSolver")
         s["Output File Name"] = sifio.FileAttr("case")
         s["Vtu Format"] = True
-        if self.unit_schema == 1:
+        if self.unit_schema == Units.Scheme.SI2:
             s["Coordinate Scaling Revert"] = True
             Console.PrintMessage(
                 "'Coordinate Scaling Revert = Logical True' was "