Dart null 与 Null

Question

As far as a know, checking if a object is null or Null should be the same thing on Dart.

Something like:

print(bar == null);
print(bar is Null);

should print the same value. But, in a flutter app using firebase I got the following behaviour:

  print(snapshot.data['appearance']['details'].runtimeType); // Null
  print(snapshot.data['appearance']['details'].runtimeType == null); // false
  print(snapshot.data['appearance']['details'].runtimeType == Null); // true
  print(snapshot.data['appearance']['details'].runtimeType is Null); // false

the field value is null on firebase. Why is it behaving like this?

Answer 1

null is a value . Null is a type .

.runtimeType returns a Type . It cannot return a null value (that would mean the object has no type). null.runtimeType returns Null ; that is, the null object has a type named Null .

As for why .runtimeType is Null is false , see: What is the difference between 'is' and '==' in Dart?