Cannot add elements into list inside map body-CodePudding

When executing the following code , no items added to list named x , Any idea why ? I know if i loop normally over it, it will work but i just wonder why it behaves like that

    List<int> x = [];
    List<int> y = [1,2,3,4];
    y.map((item) => x.add(item  2));

CodePudding user response：

The .map() method returns a lazily evaluated Iterable:

Returns a new lazy Iterable with elements that are created by calling toElement on each element of this Iterable in iteration order.

Since you don't consume the returned Iterable, it will not trigger the method provided to map() and nothing happens.

You can instead use the forEach() method which will run on each elements in your list immediately.