I just took the Kotlin badge test on LinkedIn. It ...

# announcements

[spierce7]

I just took the Kotlin badge test on LinkedIn. It doesn’t tell me the answers so I don’t know for sure. There are a LOT of small wording problems in the quiz where it’s not clear if they are trying to gotcha you or not.

i.e. They show you a function and call it shouldEqual, but the correct answer calls the function shouldMatch. There were lots of small little mistakes in the correct answers that make you question whether or not it’s the correct answer.

[spierce7]

Also why does Delegates.notNull() exist when there is lateinit ?

[ephemient]

I haven't seen that test, but Delegates.notNull() existed before lateinit, and still has some uses: for example, primitives can't be lateinit, but can be Delegates.notNull()

[spierce7]

The question was something like “If you want to have a variable that is set later, but can’t be null, what should you do?“. I wasn’t sure if Delegates.notNull() was a thing, and based on their previous mistakes I questioned whether they were referring to lateinit as a delegate. 😛 Obviously I missed that one.

[spierce7]

Is lateinit just compiling down to the raw variable access with some inlined checks before the access?

[spierce7]

oh - thats what’s happening, only they create functions instead of inlining the checks:

public static String test;

   @NotNull
   public static final String getTest() {
      String var10000 = test;
      if (var10000 == null) {
         Intrinsics.throwUninitializedPropertyAccessException("test");
      }

      return var10000;
   }

   public static final void setTest(@NotNull String var0) {
      Intrinsics.checkNotNullParameter(var0, "<set-?>");
      test = var0;
   }

[ephemient]

another important thing you can see with the lateinit var: it exposes the raw field so that Java dependency injection libraries can access it

[ephemient]

btw, if it's a private member, it is raw field accesses

[spierce7]

You have a lot of specialized lateinit knowledge. 😄 Why do you know all this off the top of your head?

[ephemient]

regarding private raw field access, that happens for all properties, not just lateinit

[ephemient]

regarding DI/backing field, that was part of the original design. https://youtrack.jetbrains.com/issue/KT-9067

[spierce7]

I guess I knew that about properties too. I just haven’t thought about it for a few years. I also haven’t used that method of DI for 4 or so years now either.