Summary
We have covered a lot of ground in this chapter, inching towards the reactive programming model. We learned about the GoF Observer pattern and understood its shortcomings. Then, we digressed into philosophy to understand the method of looking at the world from a structural, behavioral, and functional perspective. We learned about the GoF Composite/Visitor pattern in the context of modeling an expression tree. We learned how to flatten the hierarchy into a list and navigate them through the Iterator. Finally, we transformed the scheme of things a bit to reach Observables. Normally, Observables work with Streams, but in our case it was a scalar value. In the next chapter, we will learn about event Stream processing to complete our prerequisites for learning reactive programming.
