why doesn't this work: ```IconButton(onClick = navigator::popBackStack)``` where navigator.popBackS...

# getting-started

[Nick]

why doesn't this work:

IconButton(onClick = navigator::popBackStack)

where navigator.popBackStack is:

val popBackStack: () -> Unit

however, this works:

IconButton(onClick = navigator.popBackstack)

[ephemient]

isn't the message clear? if you have a val popBackStack, then ::popBackStack is a reference to the val, but you want the value

[ephemient]

if you had fun popBackStack() then you'd want ::popBackStack but you don't

[Nick]

ohhhh, its clicking in my head now. the ::popBackStack essentially be returning whatever the value in popBackstack is, whereas the the other way is just invoking it, right?

[ephemient]

no

[ephemient]

there are languages in which variables and functions use the same namespace (Type-1 Lisps, Python, Javascript, etc.) and languages in which variables and functions use different namespaces (C/C++, Java, Kotlin, etc.)

[ephemient]

while Kotlin makes it easy to call a function reference in a variable with the same syntax as a function call, it is not the same

[ephemient]

with fun popBackStack(), there is no value named popBackStack. the only way to use it is by a function call popBackStack() or reference ::popBackStack

[ephemient]

with val popBackStack, there is a value named popBackStack, not a function. Kotlin lets you write popBackStack() as a shortcut for popBackStack.invoke()

[Nick]

ahh thanks!