Scala Package && Package Objects

Scala package

scala package 和 java package作用是一样的，但scala package 又有些不同，如下示例，

package com.usoftclass Person (val firstName: String,val lastName: String,val age: Int,val occupation: String) {def fullName: String = firstName + " " + lastNamedef greet (formal: Boolean): String = {if (formal)"Hello, my name is " + fullName + ". I'm a " + occupation + "."else"Hi, I'm " + firstName + "!"}}

限定Person 类在 com/usoft 目录下。scalac 编译后会生成相应的目录。

也可以这样做，把class的定义放在package scope下，如下，

package com.usoft1{class Person (val firstName: String,val lastName: String,val age: Int,val occupation: String) {def fullName: String = firstName + " " + lastNamedef greet (formal: Boolean): String = {if (formal)"Hello, my name is " + fullName + ". I'm a " + occupation + "."else"Hi, I'm " + firstName + "!"}}
}

如下编译可以通过，Person.scala是文件名

E:\test-scala>scalac Person.scala

会生成相应的目录 com/usoft1

package的定义也可以连着写，如下，

package com.usoft
package example
package scala
class Person

其实上面的package定义就等于下面的写法，

package com.usoft.example.scala
class Person

还可以这样在同一个文件里定义两个包名，如下，

package com.usoft1{class Person (val firstName: String,val lastName: String,val age: Int,val occupation: String) {def fullName: String = firstName + " " + lastNamedef greet (formal: Boolean): String = {if (formal)"Hello, my name is " + fullName + ". I'm a " + occupation + "."else"Hi, I'm " + firstName + "!"}}
}package com.usoft2{class Student{}
}

同时也会生成相应的目录，com/usoft2

package的定义也可以嵌套，如下，

package com{package usoft{package example{class Person{}}}
}

相应的会生成com/usoft/example目录

详细：http://www.artima.com/scalazine/articles/chained_package_clauses_in_scala.html

http://www.drmaciver.com/2009/07/how-packages-work-in-scala/

package object应用示例

下面写一个package object应用的例子，

package gardening{package fruits{class Fruit(val name: String, val color: String)object apple extends Fruit("Apple", "green")object plum extends Fruit("Plum", "blue")object banana extends Fruit("Banana", "yellow") package object fruits {val planted = List(apple, plum, banana)               def showFruit(fruit: Fruit) {println(fruit.name +"s are "+ fruit.color)}}}
}// in file PrintPlanted.scala
object PrintPlanted {def main(args: Array[String]) {import gardening.fruits._for (fruit: Fruit <- fruits.planted) {showFruit(fruit)}}
}

编译运行，

E:\test-scala\package-object>scalac PrintPlanted.scalaE:\test-scala\package-object>scala PrintPlanted
Apples are green
Plums are blue
Bananas are yellowE:\test-scala\package-object>

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