attributeChangedCallback method

void attributeChangedCallback(String name, String? oldValue, String? newValue)

Called when an observed attribute changes.

Override this method to react to attribute changes at runtime. This is called:

• For each observed attribute with a value during hydration (before onMount)

• Whenever an observed attribute is added, changed, or removed

• name: The attribute name that changed

• oldValue: The previous value (null if attribute was added)

• newValue: The new value (null if attribute was removed)

Example

@override
void attributeChangedCallback(String name, String? oldValue, String? newValue) {
  switch (name) {
    case 'disabled':
      _updateDisabledState(newValue != null);
    case 'count':
      _updateCount(int.tryParse(newValue ?? '') ?? 0);
  }
}

Implementation

void attributeChangedCallback(
  String name,
  String? oldValue,
  String? newValue,
) {}