In this chapter, you will learn the core concept of objects in Dart, for example, how to create object-oriented code in Dart by using its concepts, such as interfaces, implicit interfaces, and abstract classes, as well as mixins, to add a behavior to a class. 

If you are an experienced programmer or already familiar with Java or similar languages, you can skip some parts of this chapter, as it has many similarities with the typical OOP concepts, such as inheritance and encapsulation. Some ideas, in particular, are important to verify, even if you are already familiar with the majority of OOP features, such as implicit interfaces and mixins, as they may introduce you to new concepts. 

You will also learn how to use third-party libraries to accelerate a project's development, gain an understanding of the advanced features of the Dart language to start developing multithreading apps by using callbacks and futures, and learn how to unit test your Dart code.

This chapter covers the following topics:

• Dart class definition syntax
• Abstract classes, interfaces, and mixins
• Understanding Dart libraries and packages
• Adding dependencies with pubspec.yaml
• Introducing async programming with Futures and Isolates
• Introducing unit tests