mapping custom data RxAndroid with Kotlin

问题

I am trying to convert examples from this article from Java to Kotlin. I get error from picture at Exmaple 5:

And I noticed, that without map() function I don't get this error

So, what the point of this error and how to write it right?

回答1:

The return value of a lambda in Kotlin is always the last expression in the block.

So in this case the result of

.map { it.note = it.note.toUpperCase() }

is not returning a meaningful value.

What you should do instead is this

.map { 
    it.note = it.note.toUpperCase()
    it
}

Which returns a type of Note instead of Unit.

来源：https://stackoverflow.com/questions/53509536/mapping-custom-data-rxandroid-with-kotlin