Fix "Child already has a owner" Assert

Sources/Swift/FlexLayout.swift

@@ -58,9 +58,12 @@ public final class Flex {
     //
 
     /**
-     This method adds a flex item (UIView) to a flex container. Internally the methods adds the UIView has subviews and enables flexbox.
+     Adds a flex item (`UIView`) to the receiver and returns the item's flex interface.
+
+     This method internally creates a new `UIView` instance corresponding to the flex item,
+     and is useful for adding a flex item/container when you don't need to refer to it later.
 
-     - Returns: The added view flex interface
+     - Returns: The flex interface corresponding to the added view.
      */
     @discardableResult
     public func addItem() -> Flex {
@@ -69,11 +72,12 @@ public final class Flex {
     }
 
     /**
-     This method is similar to `addItem(: UIView)` except that it also creates the flex item's UIView. Internally the method creates an
-     UIView, adds it has subviews and enables flexbox. This is useful to add a flex item/container easily when you don't need to refer to it later.
+     Adds a flex item (`UIView`) to the receiver and returns the item's flex interface.
+
+     This method enables flexbox for `view` and adds it as a subview of the receiver's associated host view.
 
-     - Parameter view: view to add to the flex container
-     - Returns: The added view flex interface
+     - Parameter view: The view to be added.
+     - Returns: The flex interface corresponding to the added view.
      */
     @discardableResult
     public func addItem(_ view: UIView) -> Flex {

Sources/YogaKit/YGLayout.mm

@@ -489,7 +489,12 @@ static void YGAttachNodesFromViewHierachy(UIView* const view) {
     if (!YGNodeHasExactSameChildren(node, subviewsToInclude)) {
       YGRemoveAllChildren(node);
       for (int i = 0; i < subviewsToInclude.count; i++) {
-        YGNodeInsertChild(node, subviewsToInclude[i].yoga.node, i);
+        YGNodeRef child = subviewsToInclude[i].yoga.node;
+        YGNodeRef parent = YGNodeGetParent(child);
+        if (parent != NULL) {
+          YGNodeRemoveChild(parent, child);
+        }
+        YGNodeInsertChild(node, child, i);
       }
     }