childBefore method Null safety

ChildType? childBefore(
  1. ChildType child
)

The previous child before the given child in the child list.

Implementation

ChildType? childBefore(ChildType child) {
  assert(child != null);
  assert(child.parent == this);
  final ParentDataType childParentData = child.parentData! as ParentDataType;
  return childParentData.previousSibling;
}