Scala: Default value for trait method not accepted-CodePudding

I have defined a method in a trait:

trait myTrait {
  def myMethod(entity: Entity = null, name: String)
}

val t = ....//concrete implementation of myTrait
t.myMethod("John")

I have provided default value of null for entity in method definition.

This give compilation error as: Type mismatch, required MyCustomClass found String

Why is it so?

CodePudding user response：

Use the name of your argument.

t.myMethod(name = "John")

It also works for case class when you want to .copy

case class MyStruct(a: String, b: String)

val a = MyStruct("foo", "bar")
val b = a.copy(b = "clazz")

Also, in scala, the presence / absence of value is usually represented by Option[T] like

def myMethod(entity: Option[Entity] = None, ... )