Scala for the Impatient, 3rd Edition

Chapter 6. Objects and Enumerations

Topics in This Chapter A1

• 6.1 Singletons

• 6.2 Companion Objects

• 6.3 Objects Extending a Class or Trait

• 6.4 The apply Method

• 6.5 Application Objects

• 6.6 Enumerations

• Exercises

In this short chapter, you will learn when to use the object construct in Scala. Use it when you need a class with a single instance, or when you want to find a home for miscellaneous values or functions. This chapter also covers enumerated types.

The key points of this chapter are:

• Use objects for singletons and utility methods.

• A class can have a companion object with the same name.

• Objects can extend classes or traits.

• The apply method of an object is usually used for constructing new instances of the companion class.

• If you don’t ...