Chapter 17 — JSON and Data Modeling

Level: intermediate Estimated time: 6 h Prerequisites: Chapter 16 — Organizing a Dart Project (and Chapters 9, 12, 13, 14) What you'll be able to do by the end: turn JSON text into typed Dart objects and your Dart objects into JSON text, while cleanly handling missing values, inconsistent types, and format errors.

17.0 — Chapter Objectives

By the end of this chapter, you will be able to:

• explain what JSON is for and why everyone uses it;
• recognize the six JSON value types;
• read and write a JSON object and a JSON array;
• list the differences between JSON and a Dart Map;
• follow JSON syntax rules (double quotes, no trailing comma);
• decode text with jsonDecode() and encode with jsonEncode();
• explain why jsonDecode() returns dynamic;
• cast a result to Map<String, dynamic> and List<dynamic>;
• write a model class with fromJson() and toJson();
• do an object → JSON → object round trip with no loss;
• handle nested objects and lists of nested objects;
• write defensive code to deal with missing values and inconsistent types;
• catch a FormatException on invalid JSON;
• convert enums and DateTimes to JSON and back;
• save and reload a game session in a JSON file;
• understand what json_serializable is for;
• connect all this to the REST APIs you will consume in Flutter.