Scala extends double arrow

问题

I was looking at the Anorm source code and for the RowParser trait it has the declaration:

trait RowParser[+A] extends (Row => SqlResult[A]) { ... }

I was curious what type (Row => SqlResult[A]) is? I haven't been able to find an explanation of the syntax anywhere.

回答1:

This is syntactic sugar for Function1 which is the same as this:

trait RowParser[+A] extends Function1[Row, SqlResult[A]] 

If you look further in the Anorm source you'll see that when the trait is implemented it has to define an apply function since it's implementing the Function1 trait.

来源：https://stackoverflow.com/questions/17434896/scala-extends-double-arrow