package com.parllay.scala.type_parameterizitor

/**

 * Created by richard on 15-8-9.

 * 第54讲：Scala中复合类型实战详解

 */

trait Compound_Type1; trait Compound_Type2;

class Compound_Type extends Compound_Type1 with Compound_Type2

object Compound_Type {

  def compound_Type(x: Compound_Type1 with Compound_Type2) = {println("Compound Type in global method")}

  def main(args: Array[String]) {

    /**

     *  new 一个复合类型

     */

    compound_Type(new Compound_Type with Compound_Type1 with Compound_Type2)

    /**

     * 创建一个object

     */

    object Compound_Type_Object extends Compound_Type1 with Compound_Type2

    compound_Type(Compound_Type_Object)

    /**

     * 利用type申明别名

     */

    type compound_Type_Alias = Compound_Type1 with Compound_Type2

    def compound_Type_Local(x: compound_Type_Alias) = println("Compound Type in local method")

    /**

     *

     */

    val compound_Type_Class = new Compound_Type

    compound_Type_Local(compound_Type_Class)

    /**

     * 复合类型中也可以包含结构类型

     */

    type Scala = Compound_Type1 with Compound_Type2 {def init(): Unit}

  }

}

/**

 * class A extends B with C with D with E

应做类似如下形式解读：

class A extends (B with C with D with E)

T1 with T2 with T3 …

这种形式的类型称为复合类型(compound type)或者也叫交集类型(intersection type)。

跟结构类型类似，可以在一个方法里声明类型参数时使用复合类型：

scala> trait X1; trait X2;

scala> def test(x: X1 with X2) = {println("ok")}

test: (x: X1 with X2)Unit

scala> test(new X1 with X2)

ok

scala> object A extends X1 with X2

scala> test(A)

ok

也可以通过 type 声明：

scala> type X = X1 with X2

defined type alias X

scala> def test(x:X) = println("OK")

test: (x: X)Unit

scala> class A extends X1 with X2

scala> val a = new A

scala> test(a)

OK

在上一篇介绍结构类型时也提到过复合类型中也可包含结构类型：

scala> type X = X1 with X2 { def close():Unit }

defined type alias X

 */