scala 类构造函数参数

Question

有什么区别:

class Person(name: String, age: Int) {
  def say = "My name is " + name + ", age " + age
}

和

class Person(val name: String, val age: Int) { 
  def say = "My name is " + name + ", age " + age
}

我可以将参数声明为 var 并稍后更改它们的值吗？例如，

class Person(var name: String, var age: Int) {

  age = happyBirthday(5)

  def happyBirthday(n: Int) {
    println("happy " + n + " birthday")
    n
  }
}

Answer 1

对于第一部分，答案是范围:

scala> class Person(name: String, age: Int) {
     |   def say = "My name is " + name + ", age " + age
     | }

scala> val x = new Person("Hitman", 40)

scala> x.name
<console>:10: error: value name is not a member of Person
              x.name

如果您使用 val、var 作为参数前缀，它们将从类外部可见，否则，它们将是私有(private)的，如上面的代码所示。

是的，您可以像平常一样更改 var 的值。