The doOn*() operators
In the previous chapter, we've used the map() operator a couple of times to just print to the console what's happening inside our Observable chains. However, this isn't very convenient. The map() operator always needs to return a value that is passed further down the chain, and it can catch only onNext signals.
That's why RxPHP has a couple of operators with the common prefix doOn*:
doOnNext(),ÂdoOnError(),ÂdoOnCompleted(): Each of these operators takes a callable as a parameter that is executed when they receive their respective signaldoOnEach(): This operator takes an instance ofÂObserverInterfaceas a parameter and executes its handlers for each signal
So these operators are very similar to the methods subscribeCallback() and subscribe(). The biggest advantage is in the way doOn* operators work internally. They never modify the value going through and just execute our callables, which is ideal for quickly debugging Observable chains or to perform side-effects without...
