4. scala-------隐式转换和隐式参数

1. 概念

隐式转换和隐式参数是Scala中两个非常强大的功能，利用隐式转换和隐式参数，

你可以提供优雅的类库，对类库的使用者隐匿掉那些枯燥乏味的细节。

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作用

隐式的对类的方法进行增强，丰富现有类库的功能

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隐式转换函数

是指那种以implicit关键字声明的带有单个参数的函数

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import java.io.File
import scala.io.Source


//隐式的增强File类的方法
class RichFile(val from: File) {
  def read = Source.fromFile(from.getPath).mkString
}

object RichFile {
  //隐式转换方法
  implicit def file2RichFile(from: File) = new RichFile(from)

}

object MainApp{
  def main(args: Array[String]): Unit = {
    //导入隐式转换
    import RichFile._
    //import RichFile.file2RichFile
    println(new File("c://words.txt").read)

  }
}

import java.awt.GridLayout

/**
  * Created by ZX on 2015/11/13.
  */
object ImplicitContext{
  //implicit def girl2Ordered(g : Girl) = new Ordered[Girl]{
  //  override def compare(that: Girl): Int = if (g.faceValue > that.faceValue) 1 else -1
  //}

  implicit object OrderingGirl extends Ordering[Girl]{
    override def compare(x: Girl, y: Girl): Int = if (x.faceValue > y.faceValue) 1 else -1
  }
}

class Girl(var name: String, var faceValue: Double){
  override def toString: String = s"name : $name, faveValue : $faceValue"
}

//class MissRight[T <% Ordered[T]](f: T, s: T){
//  def choose() = if(f > s) f else s
//}
//class MissRight[T](f: T, s: T){
//  def choose()(implicit ord: T => Ordered[T]) = if (f > s) f else s
//}

class MissRight[T: Ordering](val f: T, val s: T){
  def choose()(implicit ord: Ordering[T]) = if(ord.gt(f, s)) f else s
}

object MissRight {
  def main(args: Array[String]) {
    import ImplicitContext.OrderingGirl
    val g1 = new Girl("yuihatano", 99)
    val g2 = new Girl("jzmb", 98)
    val mr = new MissRight(g1, g2)
    val result = mr.choose()
    println(result)
  }
}