Groovy运营商如何运作？ [英] How does the Groovy in operator work?

问题描述

Groovyin运算符在不同的情况下似乎意味着不同的事情。有时候 x in y 意味着 y.contains（x），有时它似乎调用 y .isCase（x）。

Groovy如何知道要调用哪一个？ Groovy知道哪些使用.contains方法的特定类或一组类？还是由一个对象上的方法的存在引发的行为？是否有任何情况下，in运算符完全变成了其他东西？

解决方案

我做了一些实验，看起来像 运算符仅基于 isCase 方法，如以下代码所示：

  class MyList extends ArrayList {
 boolean isCase（Object val）{
 return val == 66 
} 
} 
 
 def myList = new MyList（）
 myList<< 55 
 55 in myList //返回false，但myList.contains（55）在myList中返回true 
 66 //返回true，但myList.contains（66）返回false 
  

对于JDK集合类，我想这看起来像运算符中的是基于 contains（）因为 isCase（）调用 contains（）对于这些类。

The Groovy "in" operator seems to mean different things in different cases. Sometimes x in y means y.contains(x) and sometimes it seems to call y.isCase(x).

How does Groovy know which one to call? Is there a particular class or set of classes that Groovy knows about which use the .contains method? Or is the behavior triggered by the existence of a method on one of the objects? Are there any cases where the in operator gets changed into something else entirely?

解决方案

I did some experimentation and it looks like the in operator is based on the isCase method only as demonstrated by the following code

class MyList extends ArrayList {
    boolean isCase(Object val) {
        return val == 66
    }
}

def myList = new MyList()
myList << 55
55 in myList // Returns false but myList.contains(55) returns true     
66 in myList // Returns true but myList.contains(66) returns false

For the JDK collection classes I guess it just seems like the in operator is based on contains() because isCase() calls contains() for those classes.

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