Scala functional programming: Should I use 'throw' or 'throw new'?

Question

Doing some functional programming in Scala, and coming from a Java background, I tend to throw my exceptions like this:

throw new MyException("something is wrong")

However, I've also seen people omit new:

throw MyException("something is wrong")

Which is the more idiomatic way?

It doesn't matter. If you're trying to follow best function programming/Scala practices, you should be striving to not throw exceptions, anyway. — Michael Zajac, Mar 10 '17 at 14:01
If the Exception class is an object, then you may omit it. Otherwise, you're calling the class — OneCricketeer, Mar 10 '17 at 14:04

score 6 · Accepted Answer · answered Mar 10 '17 at 14:01

6

I'd say the idiomatic way is to avoid exceptions altogether and use Either instead. Scala is a functional language. Functions should return values, not have side effects. Exceptions are side effects. Either gives you the means to define a happy path and a sad path, separately.

answered Mar 10 '17 at 14:01

Sean Patrick Floyd

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What about `Try` and `Success`? – OneCricketeer Mar 10 '17 at 14:04
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@cricket_007 Sure, what about suggesting that in an answer of your own :-) – Sean Patrick Floyd Mar 10 '17 at 14:05
Nah, I think `Either` is more broadly used without more context to the problem – OneCricketeer Mar 10 '17 at 14:07
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In 2.11, Try is properly right-biased and has functionality that supports useful semantics. With the changes to Either in 2.12, I'd use that instead as it now has decent support for the more general usage. – Iadams Mar 10 '17 at 15:03

Scala functional programming: Should I use 'throw' or 'throw new'?

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