scala类构造函数参数 [英] scala class constructor parameters

问题描述

之间有什么区别：

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

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 s，并稍后更改它们的值？例如，

Can I declare parameters as vars, and change their values later? For instance,

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

  age = happyBirthday(5)

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

推荐答案

/ p>

For the first part the answer is scope:

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

如果您在参数前面加上 val ， var

If you prefix parameters with val, var they will be visible from outside of class, otherwise, they will be private, as you can see in code above.

是的，你可以改变var的值，就像通常一样。

And yes, you can change value of the var, just like usually.

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