define your own exceptions with overloaded constructors in scala
exception, scala
Solution
Default value for `cause` is null. And for `message` it is either `cause.toString()` or null:
val e1 = new RuntimeException()
e.getCause
// res1: java.lang.Throwable = null
e.getMessage
//res2: java.lang.String = null
val cause = new RuntimeException("cause msg")
val e2 = new RuntimeException(cause)
e.getMessage()
//res3: String = java.lang.RuntimeException: cause msg
So you can just use default values:
class MyException(message: String = null, cause: Throwable = null) extends
RuntimeException(MyException.defaultMessage(message, cause), cause)
object MyException {
def defaultMessage(message: String, cause: Throwable) =
if (message != null) message
else if (cause != null) cause.toString()
else null
}
// usage:
new MyException(cause = myCause)
// res0: MyException = MyException: java.lang.RuntimeException: myCause msg
Problem
In java exceptions have at least these four constructors: ``` Exception() Exception(String message) Exception(String message, Throwable cause) Exception(Throwable cause) ``` If you want to define your own extensions, you just have to declare a descendent exceptions and implement each desired constructor calling the corresponden super constructor How can you achieve the same thing in scala? so far now I saw this article and this SO answer, but I suspect there must be an easier way to achieve such a common thing