如何在scala中获取方法列表 [英] How to get methods list in scala

问题描述

在像python和ruby这样的语言中，询问该语言其字符串类支持哪些与索引相关的方法(哪些方法的名称包含索引"一词)你可以做

In language like python and ruby to ask the language what index-related methods its string class supports (which methods’ names contain the word "index") you can do

"".methods.sort.grep /index/i

在Java中

List results = new ArrayList();  
Method[] methods = String.class.getMethods();  
for (int i = 0; i < methods.length; i++) {  
    Method m = methods[i];  
    if (m.getName().toLowerCase().indexOf("index") != -1) {  
        results.add(m.getName());  
    }  
}  
String[] names = (String[]) results.toArray();  
Arrays.sort(names);  
return names;  

你会如何在 Scala 中做同样的事情?

How would you do the same thing in Scala?

推荐答案

好奇没有人尝试过更直接的翻译:

Curious that no one tried a more direct translation:

""
.getClass.getMethods.map(_.getName) // methods
.sorted                             // sort
.filter(_ matches "(?i).*index.*")  // grep /index/i

所以，一些随机的想法.

So, some random thoughts.

• 方法"和上面的圈套之间的区别是惊人的，但从来没有人说反射是 Java 的强项.

• The difference between "methods" and the hoops above is striking, but no one ever said reflection was Java's strength.

我在上面隐藏了一些关于 sorted 的东西:它实际上需要一个 Ordering 类型的隐式参数.如果我想对方法本身而不是它们的名称进行排序，我必须提供它.

I'm hiding something about sorted above: it actually takes an implicit parameter of type Ordering. If I wanted to sort the methods themselves instead of their names, I'd have to provide it.

grep 实际上是 filter 和 matches 的组合.由于 Java 决定匹配整个字符串，即使未指定 ^ 和 $ ，这使得它变得有点复杂.我认为在 Regex 上有一个 grep 方法是有意义的，它以 Traversable 作为参数，但是...

A grep is actually a combination of filter and matches. It's made a bit more complex because of Java's decision to match whole strings even when ^ and $ are not specified. I think it would some sense to have a grep method on Regex, which took Traversable as parameters, but...

所以，这是我们可以做的:

So, here's what we could do about it:

implicit def toMethods(obj: AnyRef) = new { 
  def methods = obj.getClass.getMethods.map(_.getName)
}

implicit def toGrep[T <% Traversable[String]](coll: T) = new {
  def grep(pattern: String) = coll filter (pattern.r.findFirstIn(_) != None)
  def grep(pattern: String, flags: String) = {
    val regex = ("(?"+flags+")"+pattern).r
    coll filter (regex.findFirstIn(_) != None)
  }
}

现在这是可能的:

"".methods.sorted grep ("index", "i")

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