Tutorials ▶ Language ▶ RxJava

ReactiveX corner cases

Whether you’re new to RxJava, or have used it for a while, there’s always something new to learn. While using the framework, I learned 5 not so obvious things about RxJava that helped me maximize its potential.

This article references APIs that are available in RxJava 1.2.6

1. When to use map or flatMap

Map and flatMap are two commonly used ReactiveX operators. They’re often the first two operators you learn, and it can be confusing to figure out which one’s the right one to use.
Both map and flatMap apply a transformational function on each item emitted by an Observable. However, map only emits one item, whereas flatMap emits zero or more items.

In this example, the map operator applies the split function to each string and emits one item containing an array of strings. Use this when you want to transform one emitted item into another.

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