copying dart objects doesnt actually copy the contents of the object but gets a reference to it.

copyObject.dart

void main() {
  Foo t = Foo();
  t.a = ['a', 'b', 'c']; // some value
  t.x = 30;
  Foo t1 = t;
  t1.a = ['x', 'y', 'z'];
  t1.x = 20;
  print(t1.a); // [x, y, z]
  print(t.a); // [x, y, z]
  print(t.x);
  print(t1.x);
}

class Foo {
  List<String> a = [];
  int x = 10;
}