The value of this technique becomes more apparent when you have more number of input fields in a form. Handling it otherwise with a bunch of booleans makes the code cluttered and kind of difficult to follow. But using `.combineLatest` all that logic is concentrated in a nice compact block of code (I still use booleans but that was to make the example more readable).

Using concat, you can retrieve information from an observable first (presumably this one is fast like retrieveing from a disk cache) and show preliminary data to a user. Subsequently, when the longer running 2nd observable is complete (say a network call), you can update the results on the interface using the latest information.

For the purposes of illustration i use an in-memory `List` (not an actual disk cache), but shoot out a real network call to the github api so it gives you a feel of how this can really be applied in production apps.

a. Simple pagination