Flutter List Behaviour is not as expected - list

Question

I am making a filtering system in flutter by using two lists called mailList and filteredMailList. The first time mailList is populated, this code runs:
setState(() {
filteredMailList.clear();
filteredMailList = mailList;
});
When this has been done, it seems as though any changes that I make on mailList get replicated to filteredMailList even though I haven't executed those two lines again. For example:
//Assume that mailList = ["1", "2", "3"] and filteredMailList = []
filteredMailList = mailList
//I expect then mailList = ["1", "2", "3"] and filteredMailList = ["1", "2", "3"]
mailList.add("4")
//I expect then mailList = ["1", "2", "3", "4"] and filteredMailList = ["1", "2", "3"]
//However when this is run mailList = ["1", "2", "3", "4"] and filteredMailList = ["1", "2", "3", "4"]
Does this have something to do with the fact that I might not be giving both lists the same contents, but instead saying that they are referencing the same list?
Is there a way to make filteredMailList only contain the elements of mailList and not actually reference the exact same list, so each one can still be edited independently?

Answer 1

in your code by calling filteredMailList = mailList; you are actually removing your original filteredMailList List (you don't have any refrence to that list anymore) and changing it to the mailList. so both filteredMailList and mailList points to a single List in memory
you can create a clone list from mailList like :
filteredMailList = [...mailList]; // or filteredMailList = mailList.toList();
or keep your original refrence and copy all items from mailList
filteredMailList.clear();
filteredMailList.addAll(mailList);