3 ms·
No, they are right, it would be a sequential operation if the individual steps depended on each other which is not the case. All the four tasks will be computed
by eklavya 12y ago
No, they are right, it would be a sequential operation if the individual steps depended on each other which is not the case. All the four tasks will be computed in parallel and then aggregated to give the result.
For comprehensions reduce a lot of syntactic noise and are good to have although you need to make sure that you spawn futures outside of it.
- empirewindrush 12y agoThe issue is that this: val future1 = asyncService1() val future2 = asyncService2() val future3 = asyncService3() val future4 = asyncService4() val resultFuture:Future = for { //For-comprehension r1 <- future1 r2 <- future2 r3 <- future3 r4 <- future4 } yield (someOperation(r1, r2, r3, r4)) looks a lot like this val resultFuture:Future = for { //For-comprehension r1 <- asyncService1() r2 <- asyncService2() r3 <- asyncService3() r4 <- asyncService4() } yield (someOperation(r1, r2, r3, r4)) But the second one will be sequential. This is a common trap for new Scala futures users. You are right (as is the op below) that the first one work the way you expect. It is just easy for new users who don't understand how the de-sugaring resolves for get "caught."
- eklavya 12y agoYeah but that's my point they are doing it right.They are not falling into the trap ;)
- empirewindrush 12y agoYou are right. I jumped on it without giving the author the benefit of the doubt. This is one of those things that I personally have been burned by, and I wanted to save other from falling victim to the same mistake.