Dart: Return variable without running function - flutter

Question

I have an array of items that looks like this:
final List<Map<String, String>> dateIdeas = [
{'Description': 'Drink Cocktails','Image': 'assets/images/cocktailsfull.jpg'},
{'Description': 'Go for dinner!', 'Image': "assets/images/dinner.jpg"},
];
When the user taps a button the first item is removed from the array.
removeItem() {
setState(() {
dateIdeas.removeAt(index);
});
}
This works correctly. However, I want the user to be able to undo this action. My solution to this was to perform the following:
Have the removeItem function return what the array looked like before the removal:
Map<String, String> removeItemLiked() {
final removed = dateIdeas[index];
setState(() {
_controller.reset();
likes.add(dateIdeas[index]['Description']);
dateIdeas.removeAt(index);
});
return removed;
}
Have an undo function that adds the item back into the array at index 0:
void undo() {
setState(() {
Map<String, String> result = removeItemLiked();
dateIdeas.insert(0, result);
});
}
The issue here is that when triggering the undo function it also retriggers removeItem. How can I have the old array stored to a variable so I can always use it later on?

Answer 1

The removeItem is getting called by you within the undo function.
To prevent this, separate the function call from the removed variable.
// within stateful widget, declare 'removed'...
Map<String, String> removed;
Your other functions get modified like so;
void removeItemLiked() {
removed = dateIdeas[index];
setState(() {
_controller.reset();
likes.add(dateIdeas[index]['Description']);
dateIdeas.removeAt(index);
});
}
void undo() {
if(removed != null) {
setState(() {
dateIdeas.insert(0, removed);
});
}
}

Answer 2

You can store the removed item in a variable like lastRemoved and store it's index and value both. Here's a simple example:
class MyNums {
List<int> numbers = [123, 34, 5, 436, 56, 677];
Map<String, dynamic> lastRemoved;
removeItem(int index) {
lastRemoved = {
'index': index,
'item': numbers[index],
};
numbers.removeAt(index);
}
undoRemove() {
if (lastRemoved != null) {
numbers.insert(lastRemoved['index'], lastRemoved['item']);
}
lastRemoved = null;
}
}
Test:
main() {
MyNums nums = MyNums();
print('initial:\t\t ${nums.numbers}');
nums.removeItem(2);
print('remove from index 2:\t ${nums.numbers}');
nums.undoRemove();
print('undo index 2:\t\t ${nums.numbers}');
nums.removeItem(2);
print('remove from index 2:\t ${nums.numbers}');
nums.removeItem(2);
print('remove from index 2:\t ${nums.numbers}');
nums.undoRemove();
print('undo index 2:\t\t ${nums.numbers}');
nums.undoRemove();
print('nothing to undo:\t ${nums.numbers}');
}
Output:
initial: [123, 34, 5, 436, 56, 677]
remove from index 2: [123, 34, 436, 56, 677]
undo index 2: [123, 34, 5, 436, 56, 677]
remove from index 2: [123, 34, 436, 56, 677]
remove from index 2: [123, 34, 56, 677]
undo index 2: [123, 34, 436, 56, 677]
nothing to undo: [123, 34, 436, 56, 677]