One of the main advantages of functional reactive programming is how easy it makes reusing code, as we detach the source of data (observable) to the transformations we do on this data (operators) to the effect it causes when it happens (action taken by an observer), we can easily reuse each part of our code.
In the previous chapters, we saw how we can reuse an observable adding multiple observers to it. Now we can go one step further and combine these observables to create a new source of data; this will give us even more power.
When we combine (specifically when we concatenate) observables we can also avoid repeating code that is aligned with one of the main concepts of good code, which is Don't Repeat Yourself (DRY).
One simple and easy to understand example of combining observables to avoid subscribing to two observables can happen in a common task. Imagine that we...
