This chapter will introduce you to the basic building blocks that form the foundation of RxSwift as a library. We will introduce two different types of programming styles, the imperative and declarative style of doing things in code, and then establish the sweet spot between the two styles where RxSwift sits to take advantage of both programming paradigms.

We will elaborate on what functional reactive programming is and how you can adapt your code for it. The main topics covered in this chapter are as listed:

• Functional reactive programming: Basic building blocks, concepts, and frequently used terms
• Marble diagrams
• Railway-oriented programming