import 'dart:convert';

​

main(){

  // Define sourceA

      var sourceA = {

        "nested": {

          "value": 10

        }

      };

​

      // Define sourceB

      var sourceB = {

        "sourceA": {...sourceA}

      };

​

      // Clone both sources into two new maps

      var m1 = {...sourceA};

      var m2 = {...sourceB};

      var m3 = json.decode(json.encode(sourceB)); // deep copy

​

      print(m2["sourceA"]!["nested"] == m1["nested"]); // prints true

      print(m3["sourceA"]!["nested"] == m1["nested"]); // prints false

​

      // Check hash codes

      print(m2["sourceA"]!["nested"].hashCode); // prints 418854379

      print(m3["sourceA"]!["nested"].hashCode); // prints 892131505

      print(m1["nested"].hashCode);             // prints 418854379

​

      // Change the nested value of m3

      // m2["sourceA"]!["nested"]!["value"] = 11;

      m3["sourceA"]!["nested"]!["value"] = 11;

​

      // Observe it has been changed in m1

      print(m1["nested"]!["value"]); // prints 10

}