I was browsing through RxMarbles and was totally baffled by the sample function. The marble diagram looks pretty random at first sight:

At first I thought - “Hey, that second sequence is getting totally ignored!”. But after I read the description I figured it out:

The first sequence’s elements is what sample emits, while the second sequence’s elements determine when sample emits. So in a way yes - the actual values A, B, C, D do get totally ignored.

When it was clear to me what sample does I started wondering if this function has any practical application :]

This brought me to creating a split lap timer app to test what sample can do for me. In the finished project I have a timer emitting time values (aka the first sequence) and I want to grab (or sample) the values whenever the user taps a button (aka the second sequence).

Here’s how the marble diagram looks like for the app setup:

And this is how the app looks like when finished:

Let’s build that app :]