Flutter: Concurrent modification during iteration - flutter

Question

So I know that my mistake lies in trying to change my data when im iterating through it
this is the exact error
"Expected Non-error `Concurrent modification during iteration:
Instance of 'LinkedMap<dynamic, dynamic>'.
and this is my code:
_products.forEach((key, value) {
if (key.titel == product.titel) {
_products[key] += 1;
} else {
_products[product] = 1;
}
}
but I don't really get how I would be able to modify my data without iterating through it. Any suggestions?
----------------my Attempt -------------------
var _products = {}.obs;
var temp = {}.obs;
void addProduct(Product product) {
temp = _products;
if (_products.length > 0) {
_products.forEach((key, value) {
if (key.titel == product.titel) {
temp[key] += 1;
} else {
temp[product] = 1;
}
});
}
I get the same error; I think that is because in this line:
temp = _products;
I just get the reference on _products & I don't write _products in temp

Answer 1

So as mmcdon suggested you need make a copy of your existing thing that you want to iterate upon & iterate through that instead of your original piece
So in my case I need to do this:
var _products = {}.obs;
var temp = {}.obs;
void addProduct(Product product) {
temp = RxMap<dynamic, dynamic>.from(_products);
if (_products.length > 0) {
temp.forEach((key, value) {
if (key.titel == product.titel) {
_products[key] += 1;
} else {
_products[product] = 1;
}
});
}
So as you can see I iterate through temp, that basically is _products & Im writing the data that I need in _products