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我读斯卡拉(第二版)由Martin Odersky的书编程和我有在第一章的例子问题斯卡拉同伴对象10与抽象类
这是我的文件几乎是在结束章:
class Element
object Element {
private class ArrayElement(
val contents: Array[String]
) extends Element
private class LineElement(s: String) extends ArrayElement(Array(s)) {
override def width = s.length
override def height = 1
}
private class UniformElement(
ch: Char,
override val width: Int,
override val height: Int
) extends Element {
private val line = ch.toString * width
def contents = Array.fill(height)(line)
}
def elem(contents: Array[String]): Element =
new ArrayElement(contents)
def elem(chr: Char, width: Int, height: Int): Element =
new UniformElement(chr, width, height)
def elem(line: String): Element =
new LineElement(line)
}
abstract class Element {
def contents: Array[String]
def width: Int =
if (height == 0) 0 else contents(0).length
def height: Int = contents.length
def above(that: Element): Element =
elem(this.contents ++ that.contents)
def beside(that: Element): Element =
elem(
for (
(line1, line2) <- this.contents zip that.contents
) yield line1 + line2
)
}
编译器这样说:
defined class Element
<console>:15: error: method width overrides nothing
override def width = s.length
^
<console>:16: error: method height overrides nothing
override def height = 1
^
<console>:21: error: value width overrides nothing
override val width: Int,
^
<console>:22: error: value height overrides nothing
override val height: Int
^
<console>:17: error: not found: value elem
elem(this.contents ++ that.contents)
^
<console>:20: error: not found: value elem
elem(
^
如果我从那时候开始删除class Element
它抱怨的元素类型我当我试图对它进行子类化时,没有找到它。
我发现这里几个话题已经讨论从本章的这本书,但我不能使用任何提出的解决方案存在的。
我错过了什么?
问候, 诺伯特
谢谢你,问题是,我把进口错了地方。在书中它说我必须把它放在课外。它现在有效。 ;) – norbertk