groovy如何向Java类添加新方法？ [英] How does groovy add new methods to Java classes?

问题描述

请考虑以下片段 -

  println String.class 
  

输出是 -

 类java.lang.String 
  

我期待String的一个子类，因为它包含许多不属于Java类的成员。例如 -

  println String.methods.size（）
   
 
  methods 不是Java类的成员。
 
 
解决方案
 Groovy有一个元类注册表。当你在一个类上调用方法时，会检查注册表以查看该类实例是否存在metaClass扩展方法。
 
 
 
从标准文档 -  
 
 
每个groovy对象都有一个metaClass，用于管理该语言的动态
性质。该类拦截对groovy对象
的调用，以确保可以添加适当的grooviness。 来源 
 
 
 
Consider the following snippet - 
println String.class
The output is - 
class java.lang.String
I was expecting some subclass of String since it contains many members that are not a part of the Java class. For example - 
println String.methods.size()
methods is not a member of the Java class.

How does this magic happen?
解决方案
Groovy has a metaclass registry. When you call a method on a class the registry is inspected to see if a metaClass extension method exists for that class instance.

From the standard documentation - 

  
Each groovy object has a metaClass that is used to manage the dynamic
  nature of the language. This class intercepts calls to groovy objects
  to ensure that the appropriate grooviness can be added. Source


                        
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