Does anyone else s company not let them use anywhere no exce

Question

Does anyone else s company not let them use anywhere no exceptions

looki · Answer

Where would you need to use it I always add ` throw Exception foo ` instead so it s handled with a descriptive exception

blakelee · Answer

For me it was interop with java classes that don t have NonNull annotations

blakelee · Answer

```var x Int = null fun test Int var y = x if y == null y = someJavaFunctionThatDoesntReturnNull return 1 + y fun someJavaFunctionThatDoesntReturnNull Int = 1```

pavel · Answer

`fun test = x someJavaFunctionThatDoesntReturnNull +1`

blakelee · Answer

That works too But my use case is more complex than that

Vlad · Answer

` ` is a perfectly reasonable language feature There is nothing wrong with it Having a blanket ban on a language construct does not sound like a thought out decision

Lou Morda · Answer

yes my company does not let me double bang is a big no no

Marko Mitic · Answer

< Vlad> so `goto` is fine to use then smile

Vlad · Answer

I don t think this is a fair comparison There are lots of valid use cases for ` ` that don t bring it nowhere close to the issues usually attributed to goto

Colton Idle · Answer

This seems like a terrible rule but some people rather be in some super weird state instead of crash There are reasons to use etc Having a ban seems unreasonable There are definitely times where something should not be null and you don t want to propagate a null value saves you from NPE but will still propagate a null Causing you to have weirdness or fail further down the line further from the truth of the issue

fred.deschenes · Answer

I really don t get banning ` ` but allowing ` throw `

streetsofboston · Answer

Usually ` ` is a code smell but sometimes it is not Outright banning it makes no sense in my opinion If you do folks will do this `x throw NullPointerException ` man shrugging

tddmonkey · Answer

< Marko Mitic> `goto` did have perfectly valid use cases in C smile

Jukka Siivonen · Answer

We use checkNotNull requireNotNull which allows custom error message with more information of context if needed

Lou Morda · Answer

I was actually told not to on the interview I used them in my coding problem

wasyl · Answer

gt I really don t get banning ` ` but allowing ` throw ` To me ` ` is typically `yeah it s null but I don t care` while ` throw` requires you to think why it could be null and come up with appropriate message And in case being not null is an invariant then `checkNotNull` better conveys I know it s never null Similarly `requireNotNull` is appropriate to tell This parameter should not be null so you messed up this invocation Anyway I don t think I ve seen legitimate usage of ` ` other than being lazy and not wanting to provide message refactor code a bit It s mostly people doing `if field = null field doSomething ` too so I also get why it s difficult for some to see why it d be useful I wonder if Kotlin would have ` ` operator if it wasn t for Java interop

pavel · Answer

I looked through my code and found this `val foo Int = listOf fooService getFoo barService getBar bazService getBaz max `

pavel · Answer

the list will never be empty and it s obvious that it isn t to any reader

wasyl · Answer

thinking face I agree this looks like a reasonable usage of ` ` Personally I d still write ``listOf max let checkNotNull ` but I guess this just proves the point that some people just don t like ` ` slightly smiling face Anyway I think forbidding ` ` also serves junior developers since typically having to use it means there s something iffy with your code like the field I mentioned before

pavel · Answer

I completely agree that usually ` ` can be expressed better in other ways And having a general rule against that operator is a good idea But this rule just like most other rules has exceptions

gildor · Answer

Hmm but why do you need listOf max in this case Why not `maxOf` function

pavel · Answer

In this particular case yes But of I had 4 things or 5

yen · Answer

The point is that there are cases e g calling `max ` on a list that is never empty where you the programmer knows that some thing cannot be null but the compiler can t prove it

yen · Answer

Cases like these are where things like ` ` becomes necessary

yen · Answer

I really like the ` throw Exception ` solution for cases like these

gildor · Answer

also ` error `

gildor · Answer

gt In this particular case yes But of I had 4 things or 5 Create function `maxOf` with vararg argument I actually surprised that its not there In general it looks as a good example when I know it s not null give me my double bang should be replaced with more efficient and much more idiomatic function from stdlib or your own Even super simple extension like `maxOrThrow ` would be better because provides much better error message

gildor · Answer

But I want to be clear I m not for any restrictions in code style about this or of language I m just trying to say that many cases it s actually good recommendation to wait a second and ask yourself can I improve it by avoiding nullability or at least by providing some meaningful error message actually investigate such KotlinNullPointerExceptions is not so easy in many cases because you not always have context sometimes they are caused by Java interop and line where it crashed not always enough Also in my career I saw too many ImpossibleExceptions on prod

Stephan Schroeder · Answer

I m pretty sure this works ```fun test Int val y Int = x someJavaFunctionThatDoesntReturnNull return 1 + y ``` Can t you always assign a platform type to a non nullable type as long as you make the type of the variable explicit

gildor · Answer

Yes but it works only for Java types and only if those types are not annotated with Nullability annotations

Colton Idle · Answer

< gildor> gt also ` error ` I m unfamiliar with that What s error

gildor · Answer

< Colton Idle> This is a function from standard library also in package `kotlin` so doesn t require import

Colton Idle · Answer

< gildor> that s really helpful It s like a quick way to create a IllegalStateException with a message thumbsup TIL