Personally, I'd go with 2, which is how I dealt wi...

# announcements

[gabrielfv]

Personally, I'd go with 2, which is how I dealt with this in Java

[Shawn]

3 is just 2 with extra bones, I wouldn’t bother

[Burkhard]

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]

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]

Right. If you’re really okay with the method no-oping if passed null, then I’d say you ought to make it explicit

[Shawn]

could shorten it to obj ?: return

[enleur]

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

[gabrielfv]

Problem is that making it explicit is noneffective towards Java

[gabrielfv]

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

[Shawn]

I thought requireNotNull() doesn’t yet work with smart-casting

[Burkhard]

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

[Burkhard]

@Shawn you can use val x = requireNotNull

[Shawn]

I see

[gabrielfv]

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

[gabrielfv]

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

[gabrielfv]

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

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

[Burkhard]

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

[gabrielfv]

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

[gabrielfv]

Static analysis would probably stress that possibility, since method contract would be similar to @NonNull, but afaik it doesn't avoid anything

[Burkhard]

The kotlin compiler adds a call to Intrinsics.checkParameterIsNotNull for all parameters. This will throw an InvalidArgumentException

[neil.armstrong]

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

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

}

[gabrielfv]

Well, let allows for values returning, just would need to append an ?: defaultValue to the end