``` class A { val foo = "hello" } class B(a: A) { init { a.foo.bar // null pointer ...

# announcements

[iex]

class A {
    val foo = "hello"
}
class B(a: A) {
    init {
        a.foo.bar // null pointer
    }
}
`

[streetsofboston]

bar? Where does bar come from?

[iex]

my foo isn't a string. It's just a method of the field

[iex]

point being a.foo is null

[streetsofboston]

Could you post a snippet of the actual code so that we can see what might wrong?

[streetsofboston]

E.g. also how the constructor of the B class is called.

[iex]

hm yeah I can't reproduce it with this snippet. Will play a bit with a scratch and post if I can't figure it out

[iex]

ok, so the problem is this

class B(a: A) {
    init {
        println(a.foo.length)
    }
}

class A {
    val b = B(this)
    val foo = "hello"
}

B(A())

And the solution is to move the line with val foo = "hello" above the one that's initializing B

[Marko Mitic]

circular dependencies are a b**ch

[streetsofboston]

yes, this makes sense. foo has not yet been initialized when you access it in `B`’s constructor block

[ribesg]

Nothing unexpected here

[streetsofboston]

Try something like this. It won’t run:

open class A(val b: B)
open class B(val a: A)

object objectA : A(objectB)
object objectB : B(objectA)

If you change it to this:

open class A(val b: B?)
open class B(val a: A?)

Then the value of objectA.b or objectB.a may or may not be null… 🙂

[iex]

yeah I understand the reason... bit hairy 😄

[iex]

thanks for the help in any case!

[Stephan Schroeder]

you probably did this already, if not, just exchange the lines in A

class B(a: A) {
    init {
        println(a.foo.length)
    }
}

class A {
    val foo = "hello"
    val b = B(this)
}

B(A())

[iex]

@Stephan Schroeder yes I did 😄