hihi, does anyone knows why this works? ``` fun &...

# announcements

[aballano]

hihi, does anyone knows why this works?

fun <T> Intent.getSerializableOrDefault(name: String, default: T) =
      getSerializableExtra(name) as T ?: default

my guess is that being T a non-nullable type this should crash while trying to cast, right? But apparently in my test it works:

@Test fun `should get default`() {
        val default = ASerializableClass(2)

        assertThat(Intent().getSerializableOrDefault("a", default)).isEqualTo(default)
    }

Slack Conversation

[diesieben07]

as T is an unchecked cast, it does not actually do any check, it says "ok I'll assume this is a T now".

[aballano]

but if you do null as String it will crash

[diesieben07]

Yes, because String is a concrete type. T is a type parameter, it could be any type, it's erased.

[diesieben07]

T could be String?, too.

[aballano]

but is not in that case

[aballano]

assertThat(Intent().getSerializableOrDefault<ASerializableClass>("a", default)).isEqualTo(default) that still works

[diesieben07]

Yes, but while compiling getSerializableOrDefault the compiler does not know that.

[diesieben07]

At compile time it is not known what T is, so you cannot check for it.

[aballano]

Sorry still don't get it 😅 at the end T in my specific case is gonna be a non-nullable type because the default is not gonna be null, so either the compiler is doing some extra checks that i'm not aware of or that should crash, no?

[diesieben07]

Generics are erased. Once compiled your getSerializableOrDefault method looks like this:

fun Intent.getSerializableOrDefault(name: String, default: Any?)

[diesieben07]

And as T does nothing at runtime. There is no actual type-check performed.

[trevjones]

you can cast it to a T? so that it is more clear

[aballano]

ahhhh i see

[diesieben07]

It would still be unchecked, @trevjones

[aballano]

yep, i could use as? T or as T?, but Take is still right

[aballano]

cool thanks @diesieben07 !!

[trevjones]

checked or not doesn’t matter as much I am more concerned about it being clear what the expectation is