未定义Scala案例类的备用构造函数：没有足够的方法参数

Question

我无法弄清楚为什么这不起作用...在编译期间我收到以下错误：

[error] /Users/zbeckman/Projects/Glimpulse/Server-2/project/glimpulse-server/app/service/GPGlimpleService.scala:17: not enough arguments for method apply: (id: Long, glimpleId: Long, layerOrder: Int, created: Long, attachments: List[models.GPAttachment])models.GPLayer in object GPLayer.
[error] Unspecified value parameter attachments.
[error]     private val layer1: List[GPLayer] = List(GPLayer(1, 42, 1, 9), GPLayer(2, 42, 2, 9))

对于此案例类...请注意备用构造函数的定义：

case class GPLayer(id: Long, glimpleId: Long, layerOrder: Int, created: Long, attachments: List[GPAttachment]) {
    def this(id: Long, glimpleId: Long, layerOrder: Int, created: Long) = this(id, glimpleId, layerOrder, created, List[GPAttachment]())
}

Answer 1

请注意，在您的情况下，您可以为最后一个参数提供默认值：

case class GPLayer(id: Long, glimpleId: Long, layerOrder: Int, created: Long, attachments: List[GPAttachment] = List())