Scala underscore - ERROR: missing parameter type for expanded function

问题:

I know there have been quite a few questions on this, but I've created a simple example that I thought should work,but still does not and I'm not sure I understand why

val myStrings = new Array[String](3) // do some string initialization  // this works myStrings.foreach(println(_))   // ERROR: missing parameter type for expanded function myStrings.foreach(println(_.toString)) 

Can someone explain why the second statement does not compile?

回答1:

It expands to:

myStrings.foreach(println(x => x.toString)) 

You want:

myStrings.foreach(x => println(x.toString)) 

The placeholder syntax for anonymous functions replaces the smallest possible containing expression with a function.

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