Dart. Cant' change elements of list - arrays

Question

I can't change elements of array using anonymous function:
var collection=[0, 1, 2];
collection.forEach((c)=> c+=1);
print(collection);
This variant doesn't work eithter:
var collection = [0, 1, 2];
for (var x in collection) {
x=x+1;
}
print(collection);

Answer 1

If you wish to replace/update all items in a list (List<int> items = [1, 2, 3]):
items = items.map((x) => x + 1).toList();
for (int i = 0; i < items.length; i++) items[i] += 1;
items = List<int>.generate(items.length, (i) => items[i] + 1);
List<int> tempItems = [];
items.forEach((x) => tempItems.add(x + 1));
items = tempItems;

Answer 2

You can't change the arguments to a function or var-in loop. You can call methods on them, which might have the side effect of mutating them, but assigning directly to them will not alter the value from which they are effectively copied.

Answer 3

collection.forEach((c)=> c+=1);
In above line you are incrementing parameter by 1 and that will not affect to the list.
It's equavalent to:
collection.forEach((int c) {// in this case int because list contains int's
c = c + 1;
});
As you can see, no point of changing the value of a parameter(local variable).
Since it's 0,1,2, you can do like this: collection.forEach((c)=> collection[c] = c+1);. That is stupid way because whenever you change any value, you will get an error(out of range).
So, here are some ways that you can change list values:
The easy way:
void main() {
var collection=[0, 1, 2];
for(int i = 0; i < collection.length; i++) {
collection[i] += 1;
}
print(collection);
}
Using replaceRange:
void main() {
var collection=[0, 1, 2];
var temp = collection.map((c) => c+1).toList();
collection.replaceRange(0, collection.length, temp);
print(collection);
}