Scala的Case Classes的重载构造函数？ [英] Overload constructor for Scala's Case Classes?

问题描述

在Scala 2.8中有一种方法来重载一个case类的构造函数？

In Scala 2.8 is there a way to overload constructors of a case class?

如果是，请放一个代码片段解释，如果没有，请解释一下为什么？

If yes, please put a snippet to explain, if not, please explain why?

推荐答案

重载构造函数对于案例类不是特殊的：

Overloading constructors isn't special for case classes:

case class Foo(bar: Int, baz: Int) {
  def this(bar: Int) = this(bar, 0)
}

new Foo(1, 2)
new Foo(1)

您可能还想重载伴随对象中的 apply 方法，当您省略 new 时调用该方法。 p>

However, you may like to also overload the apply method in the companion object, which is called when you omit new.

object Foo {
  def apply(bar: Int) = new Foo(bar)
}

Foo(1, 2)
Foo(1)

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In Scala 2.8, named and default parameters can often be used instead of overloading.

case class Baz(bar: Int, baz: Int = 0)
new Baz(1)
Baz(1)

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