I think the Dialog one is cold? And the events one is definitely hot since emissions can be missed by tardy Subscribers. Sorry, now that I'm documenting this stuff I'm having double-takes with everything I thought I knew...

technically they're all cold

or at least that's how I think about them

lol

So there's a gray area it sounds like....

or warm I should say.

well it's like yes you can click on a button when not subscribed, but you can also update a DB row when your client isn't connected to the server

Conceptually, can you make an argument they are hot? Especially to Rx newbies?

it depends on your view point

sure

the mouse is moving whether you're subscribed or not

the button is clicked whether you're subscribed or not

That's exactly what I was processing in my mind... it's still happening with or without Subscribers.

hot usually implies multicast though

That's what I was suspecting.

whereas these observable have a side-effect to truly start the data flow

definitely a gray area

Okay I feel better now. This was driving me a little crazy so thanks for validating. I'll probably introduce these factories as hot, but address multicasting in a later chapter in the eBook I'm writing.

What is simplest way to emulate CompletableFuture with rx.Single? I need “hot” one-time action (without side-effects on subscirbe)

not sure if that's 100% what you need, just a guess

the first subscribe will have the effect of starting the computation

that would be instead of cache()?

.publish().autoConnect(0)

is the "hot" part

.cache()

or

replay(1)

doesn't matter here, they'll both have the same behavior because it's a single-item observable

i tend to shy away from

cache()

because people do things like

cache(1)

thinking it'll behave like

replay(1)

and then the leak a ton of memory

Ok, thanks for the explanation

@jw thanks

@jw just so I get this right. your problem with

cache(1)

is that people think it will only cache one item although it will cache all of them while

replay(1)

will really only cache one item and discard the other ones. If I have an

Observable

(say from Retrofit) that only emits one item and I use

cacheWithInitialCapacity(1)

then everything is ok?