在Scala中的for循环中赋值 [英] Value assignment inside for-loop in Scala

问题描述

这段代码是否有区别：
$ b

Is there any difference between this code:

    for(term <- term_array) {
        val list = hashmap.get(term)
        ...
    }

和： （term ...

and:

    for(term <- term_array; val list = hashmap.get(term)) {
        ...
    }

在循环内部，我正在使用类似这样的方式更改hashmap

Inside the loop I'm changing the hashmap with something like this

hashmap.put(term, string :: list)

在检查 list 的头部时，使用第二个代码片段似乎已经过时了。

While checking for the head of list it seems to be outdated somehow when using the second code snippet.

推荐答案

c $ c>语句，如：

pre $ for（i < - is; a = something; if（a））{
...
}


for (i <- is; a = something; if (a)) { ... }

以及您的列表过期的原因，是这个转换为 foreach 调用，如：

And the reason why your list is outdated, is that this translates to a foreach call, such as:

term_array.foreach {
   term => val list= hashmap.get(term)
} foreach {
  ...
}

所以当你到达...时，你的hashmap已经被改变了。另一个例子转换为：

So when you reach ..., your hashmap has already been changed. The other example translates to:

term_array.foreach {
   term => val list= hashmap.get(term)
   ...
}

这篇关于在Scala中的for循环中赋值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！