FEM: nonlinear material, fix selection for adding one

src/Mod/Fem/femcommands/commands.py

@@ -510,9 +510,26 @@ class _MaterialMechanicalNonlinear(CommandManager):
                 "Creates a nonlinear mechanical material"
             )
         }
-        self.is_active = "with_material_solid_which_has_no_nonlinear_material"
+        self.is_active = "with_material_solid"
 
     def Activated(self):
+        # test if there is a nonlinear material which has the selected material as base material
+        for o in self.selobj.Document.Objects:
+            if (
+                hasattr(o, "Proxy")
+                and o.Proxy is not None
+                and hasattr(o.Proxy, "Type")
+                and o.Proxy.Type == "Fem::MaterialMechanicalNonlinear"
+                and o.LinearBaseMaterial == self.selobj
+            ):
+                FreeCAD.Console.PrintError(
+                    "Nonlinear material {} is based on the selected material {}. "
+                    "Only one nonlinear object allowed for each material.\n"
+                    .format(o.Name, self.selobj.Name)
+                )
+                return
+
+        # add a nonlinear material
         string_lin_mat_obj = "FreeCAD.ActiveDocument.getObject('" + self.selobj.Name + "')"
         command_to_run = (
             "FemGui.getActiveAnalysis().addObject(ObjectsFem."

src/Mod/Fem/femcommands/manager.py

@@ -104,12 +104,11 @@ class CommandManager(object):
                 and self.active_analysis_in_active_doc()
                 and self.material_selected()
             )
-        elif self.is_active == "with_material_solid_which_has_no_nonlinear_material":
+        elif self.is_active == "with_material_solid":
             active = (
                 FemGui.getActiveAnalysis() is not None
                 and self.active_analysis_in_active_doc()
                 and self.material_solid_selected()
-                and self.has_no_nonlinear_material()
             )
         elif self.is_active == "with_solver":
             active = (
@@ -204,23 +203,6 @@ class CommandManager(object):
         else:
             return False
 
-    def has_no_nonlinear_material(self):
-        "check if an nonlinear material exists which is already based on the selected material"
-        for o in FreeCAD.ActiveDocument.Objects:
-            if (
-                hasattr(o, "Proxy")
-                and o.Proxy is not None
-                and o.Proxy.Type == "Fem::MaterialMechanicalNonlinear"
-                and o.LinearBaseMaterial == self.selobj
-            ):
-                FreeCAD.Console.PrintError(
-                    "{} is based on the selected material: {}. "
-                    "Only one nonlinear object for each material allowed.\n"
-                    .format(o.Name, self.selobj)
-                )
-                return False
-        return True
-
     def with_femmesh_andor_res_selected(self):
         sel = FreeCADGui.Selection.getSelection()
         if len(sel) == 1 and sel[0].isDerivedFrom("Fem::FemMeshObject"):