学习scala笔记--30 隐式转换 隐式参数

 

 

 

 

隐式转换

 

 

 

scala> class Student(name:String)

defined class Student

 

scala> import scala.language.implicitConversions

import scala.language.implicitConversions

 

scala>  implicit def  str2Student(name:String)= new Student(name)

str2Student: (name: String)Student

 

scala> def sayHello(s:Student){ println(" hello ")}

sayHello: (s: Student)Unit

 

scala> val s = new Student("tom")

s: Student = Student@17bf3182

 

scala> sayHello(s)

 hello 

 

scala> sayHello("just a test")

 hello 

 

  

 

 

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隐式转换加强现有类型

 

 

scala> class Man(val name:String)

defined class Man

 

scala> class SuperMan(val name:String){ def emitLaser=println(" emit laser ")}

defined class SuperMan

 

scala>  import scala.language.implicitConversions

import scala.language.implicitConversions

 

scala> implicit def man2superman(man:Man):SuperMan = new SuperMan(man.name)

man2superman: (man: Man)SuperMan

 

scala> 

 

scala> val s= new Man(" man ")

s: Man = Man@5d74507c

 

scala> s.emitLaser

 emit laser  

 

 

 

 

 默认会使用两种隐式转换： 一种是源或者目标类的 伴生对象内的隐式转换函数  

                          另一种是 当前程序作用域内的可以用唯一标识符表示的隐式转换函数

  

 上述两种情况找不到 就必须手动 import 

 

 

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 隐式参数

 

 

 

 

scala> class SignPen { def writ(content :String)=println(content)}

defined class SignPen

 

scala> implicit val signPen = new SignPen

signPen: SignPen = SignPen@3bf4644c

 

 

scala> def signForExam(name:String)(implicit signPen:SignPen) { signPen.writ(name+ "come to exam in time")}

signForExam: (name: String)(implicit signPen: SignPen)Unit

 

scala> 

 

scala> signForExam("tomcat")

tomcatcome to exam in time