一、概述

今天在《Scala In Programming》中学习了关于Scala的组合与继承，下面通过一个实例作为知识的巩固。

二、实例展示

1、实例名称：

根据给定的边界值，画出一个螺旋。

2、实例描述：

a、首先给出四个类：Element、ArrayElement、UniformElement、LineElemnt，其中Element为抽象的超类，其余三个类分别继承于Element。

import scalaDemo.Element._/*** Created by user on 2016/1/18.*/
abstract class Element {def contents: Array[String]def height: Int = contents.lengthdef width: Int = contents(0).lengthdef above(that: Element): Element = {val thisParam = this widen that.widthval thatParam = that widen this.widthelem(thisParam.contents ++ thatParam.contents)}def beside(that: Element): Element = {val thisParam = this highten that.heightval thatParam = that highten this.heightelem(for((line1,line2) <- thisParam.contents zip thatParam.contents)yield line1 + line2)}def widen(w: Int): Element = {if(w <= width) this else{val left = elem(' ',(w - width)/2,height)val right = elem(' ', w - width - left.width, height)left beside this beside right}}def highten(h: Int): Element = {if(h <= height){this}else{val top = elem(' ', width, (h - height)/2)val bot = elem(' ', width, h - height - top.height)top above this above bot}}override def toString = contents.mkString("\n")
}

/*** Created by user on 2016/1/18.*/
class ArrayElement(contentsParam: Array[String]) extends Element{override def contents: Array[String] = {contentsParam}
}

/*** Created by user on 2016/1/18.*/
class UniformElement(char: Char, width: Int, height: Int) extends Element{private val line = char.toString * widthoverride def contents: Array[String] = {Array.apply(line + ": " + height)}
}

/*** Created by user on 2016/1/18.*/
class LineElement(line: String) extends Element{override def contents: Array[String] = {Array.apply(line)}
}

b、定义一个object：Element

import scalaDemo.classes.{ArrayElement, LineElement, UniformElement, Element}/*** Created by user on 2016/1/18.*/
object Element {def elem(contents: Array[String]): Element = {new ArrayElement(contents)}def elem(char: Char, width: Int, height: Int): Element = {new UniformElement(char,width,height)}def elem(line: String): Element = {new LineElement(line)}
}

c、测试实例

import scalaDemo.Element.elem
import scalaDemo.classes.Element/*** Created by user on 2016/1/18.*/
object Spiral{val space = elem(" ")val corner = elem("+")def spiral(edges: Int, direction: Int): Element = {if(edges == 1){elem("+")}else{val sp = spiral(edges - 1, (direction + 3) % 4)def verticalBar = elem('|',1,sp.height)def horizontalBar = elem('-',sp.width,1)if(direction == 0){(corner beside horizontalBar) above (sp beside space)}else if(direction == 1){(sp above space) beside (corner above verticalBar)}else if(direction == 2){(space beside sp) above (horizontalBar beside corner)}else{(verticalBar above corner) beside (space above sp)}}}def main (args: Array[String]) {val constents = new Array[String](3)constents(0) = "AAAAAAA" + ","constents(1) = "BBBBBBB" + ","constents(2) = "CCCCCCC"println(spiral(constents.length,3))}
}

三、测试结果

请查看附件中的图片