Say I want to convert following collection to List<int>,
final listDouble = <double>[1.0, 2.0];
I can either use
final listInt = List<int>.from(listDouble);
or
final listInt = listDouble.map<int>((e) => e.toInt()).toList();
Is there any difference between two approaches?
In addition to the laziness mentioned by iDecode's answer, you should be aware that the List<E>.from way isn't technically correct for your case.
List<E>.from requires that the argument list have elements of type E, and ints aren't doubles. (Note that it will work for web platforms (e.g. DartPad), where Dart is transpiled to JavaScript, because all JavaScript numbers are IEEE-754 double-precision floating point numbers. If you try it in a Dart VM, however, it will throw an exception.)
double to int, in that case it would work, correct?
double to int or int to double. Neither derives from the other, so they aren't implicitly convertible.List<E>.from requires that the argument list have elements of type E?List<int>.from requires that the argument already be a collection of ints. List<int>.from is basically the same as List<int>.of except .from is from before Dart had compile-time type-checking, so .from will fail at runtime if the argument type is wrong.Yes, there is a difference.
map() returns a lazy Iterable, meaning that the supplied function is called only when the elements are iterated unlike List.from().