[문법] While문에서 assignment 불가능

while ((c = inputStream!!.read()) != -1) {
    outputStream.write(c)
}

이거 안되서 한참 고민. Kotlin은 while안에서 assign이 안된다.

do{
    c = inputStream.read()
    outputStream.write(c)
} while(c != -1)

이렇게 고치면 가능.

사람들은 이런 의견을 내고 있다.

Wasabi375

May 11

The Kotlin team decided against it for a few reasons I think. In most cases it is just considered bad style and it also makes code harder to read. Yes your example is the one valid place where this kind of feature would be pretty handy, but they decided against it still, because only a small numbers of libraries would actually use something like this and it’s not worth adding an new feature to the language just for that.
Also there is a massive discussion about this here

 Assignment not allow in while expression?

Hi, In Java, I can do thing like this: `` BufferedReader reader = new BufferedReader(reader); String line = null; while ((line = reader.readLine()) != null) {   System.out.println(line); } However in Kotlin such thing is not allowed. I get error like “Assignments are not expressions, and only expressions are allowed in this context” So the best I can come up with is something like this, but I wonder is there a better to write this in Kotlin? I like the Java syntax better because it’s sh…

출처: https://discuss.kotlinlang.org/t/why-i-cant-apply-value-inside-while-loop/7762/2