如何在scala变更中创建变量？

Question

所以我有这个变量，currentPartNumber，它开始等于0.我想要发生的是在我的函数中，如果变量等于零，它将更改为1，并将文本打印出来。我的第二个功能是一样的 - 如果在我的第一个功能中变量变为1，并且等于1，我希望变量变为2，打印出文本。

问题是：如何让我的变量随每个函数调用而改变？

var currentPartNumber = 0 

def roomOne():Unit = { 
    if (currentPartNumber < 1) { 
     var currentPartNumber = 1 
     println("You now have parts 1 of 4.") 
    } else { 
     println("This part cannot be collected yet.") 
    { 
    } 


def roomTwo():Unit = { 
    if (currentPartNumber = 1) { 
     var currentPartNumber = 2 
     println("You now have parts 2 of 4.") 
    } else { 
     println("This part cannot be collected yet.") 
    { 
    } 

Answer 1

不要隐藏变量：从函数内部删除var。

的var关键字声明一个新构件/变量。在这种情况下，名称是阴影相同的外部变量范围。因此赋值（作为声明的一部分）对外部变量没有影响。

// no var/val - assignment without declaration 
currentPartNumber = 2 

参见：

• Why does a scala try block allow variables from the enclosing scope to be redefined?
• Why does Scala support shadow variables?

Answer 2

的一类，其中roomOne()和roomTwo()可以访问和修改其声明currentPartNumber。

class Parts{ 
    var currentPartNumber = 0 

    def roomOne():Unit = { 
    if (currentPartNumber < 1) { 
     currentPartNumber = 1 
     println("You now have parts 1 of 4.") 
    } else { 
     println("This part cannot be collected yet.") 
    } 
    } 

    def roomTwo():Unit = { 
    if (currentPartNumber == 1) { 
     currentPartNumber = 2 
     println("You now have parts 2 of 4.") 
    } else { 
     println("This part cannot be collected yet.") 
    } 
    } 
} 



scala> :load Parts.scala 
Loading Parts.scala... 
defined class Parts 
scala> var parts = new Parts 
parts: Parts = Parts@5636a67c 
scala> parts.currentPartNumber 
res0: Int = 0 
scala> parts.roomOne 
You now have parts 1 of 4. 
scala> parts.roomTwo 
You now have parts 2 of 4.