Saving Data in Flutter

Jan 31 2024 · Dart 3, Flutter 3.10, Visual Studio Code

Part 3: Reading & Writing Files

16. Using JSON (Part 1)

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There’s a small change we can implement in our app, that will have no impact on the user experience, but can have several benefits for us as developers: it’s leveraging Dart objects and JSON instead of storing simple data in SharedPreferences.
I’ve told you previously, that SharedPreferences only accepts simple data, like strings, numbers, and Booleans, and this is the way we are using SharedPreferences right now.

class AppSettings { 
  String listName = ''; 
  int calories = 0; 
  bool showFileSize = false; 
  bool showDate = false; 
} 
Map<String, dynamic> toJson() { 
    return <String, dynamic>{ 
      'listName': listName, 
      'calories': calories, 
      'showFileSize': showFileSize, 
      'showDate': showDate, 
    }; 
  } 
AppSettings.fromJson(Map<String, dynamic> json) 
  : listName = json['listName'] is String 
        ? json['listName'] as String 
        : 'My Recipes', 
    calories = json['calories'] is int ? json['calories'] as int : 2000, 
    showFileSize = 
        json['showFileSize'] is bool ? json['showFileSize'] as bool : true, 
    showDate = json['showDate'] is bool ? json['showDate'] as bool : true;