Using Subject for cascading lists

So, what's the point? Why should we use Subjects over Observables? That's actually a quite deep question. There are many ways of solving most streaming-related problems; problems where it is tempting to use a Subject can often be solved through some other way. Let's have a look at what you could be using it for, though. Let's talk about cascading drop-down lists. What we mean by that is that we want to know what restaurants exist in a city. Imagine, therefore, that we have a drop-down list that allows us to select what country we are interested in. Once we select a country, we should select the city we are interested in from a drop-down list of cities. Thereafter, we get to select from a list of restaurants, ...

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