Flutter & Shared Preferences : How do I save a list (of object) to local memory?

Question

I want to save a list of objects into my local memory using the shared_preferences package.

Let's assume that this is my class:

class Person{
   String name;
   String age;
   String gender;
}

How do I do that with shared_preferences?

I am looking forward to hearing from all of you. Thank you.

Answer 1

You can save a List<String> with shared_preferences. Therefore, we need to convert the Person class, and its list, into a String by encoding them as JSON:

class Person {
    String name;
    String age;
    String gender;
    Person({this.name, this.age, this.gender});

    factory Person.fromJson(Map<String, dynamic> parsedJson) {
        return new Person(
            name: parsedJson['name'] ?? "",
            age: parsedJson['age'] ?? "",
            gender: parsedJson['gender'] ?? "");
    }

    Map<String, dynamic> toJson() {
        return {
          "name": this.name,
          "age": this.age,
          "gender": this.gender,
        };
    }
}

void _savePersons(List<Person> persons) async {
   SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
   List<String> personsEncoded = persons.map((person) => jsonEncode(person.toJson())).toList();
   await sharedPreferences.setStringList('persons', personsEncoded );
}

In the same fashion, we can get the saved List<Person> as a JSON object and de-serialize it:

List<Person> _getPersons(List<Person> persons) async {
   SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
  final persons = await sharedPreferences.setStringList('persons', accounts);
   return persons.map((person) => Person.fromJson(person)).toList();
}