Scala隐式转换实战

来源：互联网发布：王珊数据库第五版视频编辑：程序博客网时间：2024/05/22 14:14

隐式方法
隐式参数
隐式类
隐式对象

隐式方法

import scala.io.Sourceimport java.io.Fileclass RichFile (val file : File){  def read = Source.fromFile(file.getPath)}//导入隐式方法之后file自动会转换至RichFileobject Context {  implicit def file2RichFile (file : File) = new RichFile(file)}object Hello_implicit {  def main(args: Array[String]): Unit = {    import Context.file2RichFile    println(new File("E:\\Hello.txt").read)  }}

隐式参数

object Context_implicits{  implicit val default : String = "Java"}object Param{  //声明隐式参数后会在作用域范围内导入默认的参数  def print(content : String)(implicit language : String){    println(language + " : " + content)  }}object implicit_Parameters {  def main(args: Array[String]): Unit = {    Param.print("Spark")("Scala")    import Context_implicits._    Param.print("Hadoop")  }}

隐式类

object Context_Helper{  implicit class FileEnhancer(file : File){    def read = Source.fromFile(file.getPath)  }  implicit class Op (x : Int){    def add (second : Int) = x + second  }}object implicit_class {  def main(args: Array[String]): Unit = {    import Context_Helper._    println(1.add(2))    println(new File("E:\\Text.txt").read)  }}

隐式对象

abstract class Template[T]{  def add(x : T, y : T) : T}abstract class SubTemplate[T] extends Template[T]{  def unit : T}object implicit_object {  def main(args: Array[String]): Unit = {    implicit object StringAdd extends SubTemplate[String]{      def add(x : String, y : String) : String = x concat y      def unit : String = ""    }    implicit object IntAdd extends SubTemplate[Int]{      def add(x : Int, y : Int) : Int = x + y      def unit : Int = 0    }    def sum[A](xs : List[A])(implicit m : SubTemplate[A]) : A =      if (xs.isEmpty) m.unit      else m.add(xs.head, sum(xs.tail))    println(sum(List(1, 2, 3)))    println(sum(List("a", "b", "c")))  }}

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