Implements an empty() classmethod for multiref datahandlers

Return the value of this datahandler when empty

lodel/leapi/datahandlers/base_classes.py

@@ -368,6 +368,12 @@ class MultipleRef(Reference):
     def __init__(self, max_item = None, **kwargs):
         self.max_item = max_item
         super().__init__(**kwargs)
+    
+    ##@brief Method designed to return an empty value for this kind of 
+    #multipleref
+    @classmethod
+    def empty(cls):
+        return None
 
     ##@brief Check and cast value in appropriate type
     #@param value *

lodel/leapi/datahandlers/references.py

@@ -17,6 +17,10 @@ class List(MultipleRef):
     def __init__(self, max_length = None, **kwargs):
         super().__init__(**kwargs)
 
+    @classmethod
+    def empty(cls):
+        return list()
+
     ##@brief Check and cast value in appropriate type
     #@param value *
     #@throw FieldValidationError if value is unappropriate or can not be cast 
@@ -37,6 +41,10 @@ class Set(MultipleRef):
     def __init__(self, **kwargs):
         super().__init__(**kwargs)
 
+    @classmethod
+    def empty(cls):
+        return set()
+
     ##@brief Check and cast value in appropriate type
     #@param value *
     #@throw FieldValidationError if value is unappropriate or can not be cast 
@@ -57,6 +65,10 @@ class Map(MultipleRef):
     def __init__(self, **kwargs):
         super().__init__(**kwargs)
 
+    @classmethod
+    def empty(cls):
+        return dict()
+
     ##@brief Check and cast value in appropriate type
     #@param value *
     #@throw FieldValidationError if value is unappropriate or can not be cast 
@@ -81,6 +93,10 @@ class Hierarch(MultipleRef):
                             max_childs = max_childs,
                             **kwargs)
 
+    @classmethod
+    def empty(cls):
+        return tuple()
+
     ##@brief Check and cast value in appropriate type
     #@param value *
     #@throw FieldValidationError if value is unappropriate or can not be cast