Flutter projects can have cross-platform code and platform-specific code. Cross-platform code is written in Dart. Sufficient knowledge of Dart is a prerequisite for building Flutter apps. Details of Dart language is out of the scope of this book. You can find plenty of online resources related to Dart. However, it's still very helpful to cover essential part of Dart for building Flutter apps. Recipes in this chapter cover different aspects of Dart. You can skip this chapter if you are confident about your knowledge of Dart.