class Singleton {
static final Singleton _instance = Singleton._internal();
factory Singleton() => _instance;
Singleton._internal();
}
// Whenever you need to get the singleton, call its factory constructor, e.g.:
// var singleton = Singleton();
//
// You'll always get the same instance.main() {
var s1 = Singleton();
var s2 = Singleton();
print(identical(s1, s2)); // true
print(s1 == s2); // true
}