While developing applications, it's a common situation to combine data from multiple sources before using them. One such situation is when you are building some offline application following an offline-first approach, and you want to combine the resultant data you got from the HTTP call with the data from the local database.
Now, without wasting much time, let's take a look at the operators that can help us combine producers:
- startWith()
- merge(), mergeDelayError()
- concat()
- zip()
- combineLatest()
Basically, there are a few mechanisms to combine producers (Observables/Flowables). They are as follows:
- Merging producers
- Concatenating producers
- Ambiguous combination of producers
- Zipping
- Combine latest
We will discuss all the previously mentioned techniques to combine producers in this chapter. However, let's start with an operator that we are already aware of.