Kotlin: Method reference not working?
Starting from Kotlin 1.1 writer::append
is a perfectly valid bound callable reference.
However, you still cannot write string.forEach(writer::append)
because Writer#append
method returns a Writer
instance and forEach
expects a function that returns Unit
.
For now, Kotlin only supports references to top-level and local functions and members of classes, not individual instances. See the docs here.
So, you can say Writer::append
and get a function Writer.(Char) -> Writer
, but taking a writer
instance and saying writer::append
to get a function (Char) -> Writer
is not supported at the moment.
I am using Kotlin 1.3 and while referencing a Java method I got a very similar error. As mentioned in this comment, making a lambda and passing it to the forEach
method is a good option.
key.forEach { writter.append(it) }
Being it
the implicit name of a single parameter.