Using Null Safety in classes

While you’ve seen the basics of null safety in the previous recipe, you should also be aware of a few rules that should drive the way you design classes in Dart.

Getting ready

Create a new pad in DartPad and remove the default code in the main method.

How to do it...

Let’s see an example of a plain Dart class, with two properties. Follow these steps:

1. Add a new class, with two Strings and no value:

   class Person {
     String name;
     String surname;
   }
   

2. Note the compile error saying that the two fields are non-nullable.
3. In the Person class, create a constructor that gives a value to the fields:

     Person(this.name, this.surname);  
   

4. Note that the error is now fixed.
5. Add a named constructor that takes a map of String, dynamic and creates an instance of Person:

   Person.fromMap(Map<String, dynamic> map) {
       name = map['name'];
       surname = map...