（二）scala构造器和伴生对象

构造器的使用

调用apply方法时.apply可以省略

object Hello{
	def main(args:Array[String]){
		//println("hello world")
		
		val m1 = new Man("Zhangsan")
		
    //   会报错
    //   m.apply("zhu")

		val list = List("aa", "bb")
		//调用的是伴生对象中的apply
		val m2 = Man("Wangwu")
		println("000000000000000000000");
		//调用的是class中的apply
		m2("liu", 33)
	}
}

//如果没有显示定义构造方法，编译器会分配一个默认的（不带参数）主构造器
//主构造器跟在类名后面
class Man(var name:String){
  //被主构造器调用  
  //println(name)

  var id:Int = 0
  var age:Int = 0
  
  //辅助构造器,第一行代码必须是对主构造器或者另外一个辅助构造器的调用
  def this(name:String, id:Int){
    this(name)
    this.id = id
  }
  
  def this(name:String, id:Int, age:Int){
    this(name,id)
    //this.id = id
    this.age = age
  }
  

//  def apply(name:String,id:Int): Unit = {
//    println("Unit")
//  }

  //也可以返回list
//  def apply(  name: String,id:Int): List[String] = List("ds","werfew")

   def apply(name:String,id:Int):Man= new Man(name,id)
}

object Man{
  def apply(name:String): Man = {
    new Man(name,id)
//    println("object Man")
// def apply(name:String):Man = new Man(name)
}

apply方法的使用

object apply {
  def main(args: Array[String]): Unit = {
    val anyObject = new SomeClass
    println(anyObject("key1"))
    
    val ss = SomeClass("aa")
    println(ss)
    
    val email = EMail("fantasia", "sina.com")
    println(email)
    val email2 = new Email
    email2("Test")
  }
}

class SomeClass {
    println("SomeClass ........");
    def apply(key: String): String = {
        println("SomeClass apply()" + key)
        key
    }
}

object SomeClass{
  def apply(a:String){
    println("SomClass object apply()" + a)
  }
}

class Email{
  def apply(x:String){
    println("Email apply");
    println(x);
  }
}

object EMail {
    def apply(user: String, domain: String): String = {
        println("Email Object apply()")
        user + "@" + domain
    }
}

 

unapply的使用

object Apply_unapply {
    def main(args: Array[String]): Unit = {

    val currency = Currency(30.2, "EUR")

    currency match {
      case Currency(amount, "USD") => println("$" + amount)
      case _ => println("No match.")
    }
  }
}


class Currency(val value: Double, val unit: String) {

}

object Currency{
  def apply(value: Double, unit: String): Currency = new Currency(value, unit)
  
  def unapply(currency: Currency): Option[(Double, String)] = {
    if (currency == null){
      None
    }
    else{
      Some(currency.value, currency.unit)
    }
  }
}