scala：抽象类实例化？ [英] scala: abstract classes instantiation?

问题描述

如何实例化一个抽象类？

How it comes that I instantiate an abstract class?

  abstract class A {
    val a: Int
  }

  val a = new A {val a = 3}

还是隐式创建了一些具体的类？ 新A 之后的括号是什么意思？

Or is some concrete class implicitly created? And what do those braces after new A mean?

推荐答案

，则隐式扩展 A 。您所做的是语法糖，等效于此：

With this, you implicitly extend A. What you did is syntactic sugar, equivalent to this:

class A' extends A {
    val a = 3
}
val a = new A'

这些括号仅允许您扩展a类，创建一个新的匿名类，该类实例化值 a ，因此不再抽象。

These brackets merely let you extend a class on the fly, creating a new, anonymous class, which instantiates the value a and is therefore not abstract any more.

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