Personally I d go with 2 which is how I dealt with this in J kotlinlang #announcements

I think option 1 is the best solution. I sometimes use option 2 if I have a function that should execute some optional behaviour. But if a function depends on a non null value it should fail, when called with null

gabrielfv

10/19/2018, 3:24 PM

With the assignment notation, somewhat. I'm thinking readability here, and having either a whole extra closure wrapping around or such notation seems suboptimal to me

Shawn

10/19/2018, 3:25 PM

Right. If you’re really okay with the method no-oping if passed

null

, then I’d say you ought to make it explicit

could shorten it to

obj ?: return

👍 1

enleur

10/19/2018, 3:26 PM

fun method(obj: Class?) {
    requireNotNull(obj)
    // ...
}

👍 2

gabrielfv

10/19/2018, 3:26 PM

Problem is that making it explicit is noneffective towards Java

Nice one, @enleur, didn't know about that

Shawn

10/19/2018, 3:27 PM

I thought

requireNotNull()

doesn’t yet work with smart-casting

Burkhard

10/19/2018, 3:27 PM

I don’t like @enleur’s variant. Now the function contract says that it accepts

null

but the function actually fails.

👆 4

@Shawn you can use

val x = requireNotNull

Shawn

10/19/2018, 3:28 PM

I see

gabrielfv

10/19/2018, 3:28 PM

It could work as an interoperability operator when you use an already non-null argument

It would avoid Java nulls to pass through, which is nice, but not work as an assertion, thus why smart-cast isn't applied

So, what I understood is that it should be used like that:

fun method(obj: Class) {
    requireNotNull(obj)
    // ...
}

Burkhard

10/19/2018, 3:31 PM

You don’t need any null checks if you declare the argument as notNull. The compiler adds them automatically.

gabrielfv

10/19/2018, 3:32 PM

And what happens if java code calls the method with what happens to be a null object?

Static analysis would probably stress that possibility, since method contract would be similar to

@NonNull

, but afaik it doesn't avoid anything

Burkhard

10/19/2018, 3:35 PM

The kotlin compiler adds a call to

Intrinsics.checkParameterIsNotNull

for all parameters. This will throw an

InvalidArgumentException

👍 3

neil.armstrong

10/19/2018, 3:35 PM

Could do it as an expression if don’t want to return anything

fun method(obj: Class?) = obj?.let {

}

gabrielfv

10/19/2018, 4:02 PM

Well, let allows for values returning, just would need to append an

?: defaultValue

to the end

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