Flutter: ListView.builder's trailing IconButton alters items list without being asked to-CodePudding

I have two identical lists initiated with the same data: freeBooks and updatedFreeBooks.
I am trying to return a ListView.Builder made of elements from the freeBooks List.
Each ListTile has a trailing IconButton which removes the item from the updatedFreeBooks List, but NOT from the freeBooks List.
YET for some reason pressing the trailing IconButton is also removing the element from the freeBooks list and updating the ListView WITHOUT BEING ASKED TO. WHY???

How can I ensure that the code doesn't alter the original freeBooks List? Here's the code sample:

                                  child: ListView.builder(
                                      itemCount: freeBooks.length,
                                      itemBuilder: (context, index) {
                                        String novelTitle = novel.title;
                                        return ListTile(
                                          title:
                                              Text('$novelTitle'),
                                          trailing: IconButton(
                                              onPressed: () {
                                                setState(() {
                                                  updatedFreeBooks
                                                      .removeAt(index);
                                                });
                                              },
                                              icon: Icon(Icons.cancel)),
                                        );
                                      }),

CodePudding user response：

Use updatedFreeBooks=List.of(user.fbooks)

Objects are passed by reference. When you do list1 = list; and list2 = list;, you're assigning the reference of list to both list1 and list2. So changing the object at that reference will change the data you see at all of these different variables.