fix parent setter

OrtnerMichael · OrtnerMichael · commit e882fc271337 · 2022-03-24T10:38:18.000+01:00
diff --git a/magpylib/_src/input_checks.py b/magpylib/_src/input_checks.py
@@ -143,6 +143,23 @@ def validate_field_lambda(val, bh):
     return val
 
 
+def check_input_parent(inp):
+    """
+    parent input must be None or Collection.
+    return - true if its a collection
+           - false if its None
+    raise error if neither
+    """
+    if (getattr(inp, "_object_type", "") == "Collection"):
+        return True
+    elif inp is None:
+        return False
+
+    raise MagpylibBadUserInput(
+        "Input `parent` must be `None` or a `Collection` object."
+        f"Instead received {type(inp)}."
+    )
+
 #################################################################
 #################################################################
 # CHECK - FORMAT
diff --git a/magpylib/_src/obj_classes/class_BaseGeo.py b/magpylib/_src/obj_classes/class_BaseGeo.py
@@ -12,8 +12,8 @@
 from magpylib._src.input_checks import (
     check_format_input_orientation,
     check_format_input_vector,
+    check_input_parent,
 )
-from magpylib._src.exceptions import MagpylibBadUserInput
 
 from magpylib._src.utility import add_iteration_suffix
 
@@ -142,17 +142,14 @@ def parent(self):
 
     @parent.setter
     def parent(self, inp):
-        if inp is None:
-            if self._parent is not None:
-                self._parent.remove(self)
-                self._parent = None
-        elif getattr(inp, "_object_type", "") == "Collection":
-            inp.add(inp)
-        else:
-            raise MagpylibBadUserInput(
-                f"The `parent` property of {type(self).__name__} must be a Collection."
-                f"Instead received {inp!r} of type {type(inp).__name__}"
-            )
+        is_collection = check_input_parent(inp)
+
+        if self._parent is not None:
+            self._parent.remove(self)
+            self._parent = None
+
+        if is_collection:
+            inp.add(self)
 
     @property
     def position(self):
diff --git a/magpylib/_src/obj_classes/class_Collection.py b/magpylib/_src/obj_classes/class_Collection.py
@@ -190,9 +190,8 @@ def add(self, *children, override_parent=False):
 
         Parameters
         ----------
-        children: source, `Sensor` or `Collection` objects or arbitrary lists thereof
+        children: sources, sensors or collections or arbitrary lists thereof
             Add arbitrary sources, sensors or other collections to this collection.
-            Duplicate children will automatically be eliminated.
 
         Returns
         -------
@@ -216,7 +215,7 @@ def add(self, *children, override_parent=False):
         obj_list = check_duplicates(obj_list)
         # assign parent
         for obj in obj_list:
-            if obj._parent is None or override_parent:
+            if (obj._parent is None) or override_parent:
                 obj._parent = self
             else:
                 raise ValueError(
@@ -284,7 +283,7 @@ def _remove(parent, child, recursive=True, issearching=False):
             raise ValueError(f"""{parent}.remove({child}) : {child!r} not found.""")
 
     def remove(self, child, recursive=True):
-        """Remove a specific child from the collection.
+        """Remove a specific object from the collection tree.
 
         Parameters
         ----------
