dart: dynamic List类型转换

import 'dart:async';

Stream get asynchronousNaturals async* {
  print("Begin");

  int k = 0;
  while (k < 3) {
    print("Before Yield");
    yield k++;
  }

  print("End");
}

void testAsync() {
  StreamSubscription subscription = asynchronousNaturals.listen(null);
  subscription.onData((value) {
    print(value);
    //subscription.pause();
  });
}

main() {
  var numbers = [1, 2.3, 4]; // List<num>.
  numbers.removeAt(1); // Now it only contains integers.
  var ints = new List<int>.from(numbers);
  print(ints);

  var map1 = {
    "first": ["Dart", "aaaa"],
    1: true,
    true: "2"
  };
  print(map1);

  //List list = (map1["first"] as List)?.map((e) => print(e))?.toList();
  print(map1["first"].runtimeType);
  if (map1["first"] is List) {
    List list = map1["first"] as List;
    print(list);
  }

  var a = [1, 2, 'three'];
  print(a is List); // True
  print(a is List<int>); //真的！
  print(a is List<String>); //真的！

  var b = new List<int>.from([1, 2, 3]);
  print(b is List); // True
  print(b is List<int>); // True
  print(b is List<String>); // False
}

运行结果

[Running] dart "d:\mygo\mydart\async_star_sub.dart"
[1, 4]
{first: [Dart, aaaa], 1: true, true: 2}
List<String>
[Dart, aaaa]
true
false
false
true
true
false