Groovy元编程 - 将静态方法添加到Object.metaClass [英] Groovy meta-programming - adding static methods to Object.metaClass

问题描述

当将静态方法foo（）添加到类FooBar中时，那么FooBar.foo（）按预期工作：

  FooBar.metaClass.static.foo = {
 printlnhello 
 
 FooBar.foo（）
  

然而，我反而添加了相同的静态方法foo（）到类Object中，然后FooBar.foo（）失败并带有MissingMethodException：

  Object.metaClass.static .foo = {
 printlnhello
} 
 FooBar.foo（）
 // groovy.lang.MissingMethodException：
 //方法的签名：FooBar .foo（）适用于参数类型：
 //（）values：[] 
  

为什么呢？不应该 Object.metaClass.static.foo = {..} 将foo（）也添加到FooBar中？

解决方案

为了获得您要查找的行为，您需要调用ExpandoMetaClass.enableGlobally（）

请记住这比普通的元编程有更大的内存占用。

http://groovy.codehaus.org/api/groovy/lang/ExpandoMetaClass.html#enableGlobally（）

I've encountered a Groovy meta-programming problem which I'm unable to solve.

When adding the static method foo() to the class FooBar, then FooBar.foo() works as expected:

FooBar.metaClass.static.foo = {
    println "hello"
}
FooBar.foo()

However, I instead add the same static method foo() to the class Object, then FooBar.foo() fails with an MissingMethodException:

Object.metaClass.static.foo = {
    println "hello"
}
FooBar.foo()
// groovy.lang.MissingMethodException:
// No signature of method: FooBar.foo() is applicable for argument types: 
// () values: []

Why is that? Shouldn't Object.metaClass.static.foo = { .. } add foo() also to FooBar?

解决方案

In order to get the behavior you're looking for you need to call ExpandoMetaClass.enableGlobally()

Keep in mind doing this has a bigger memory footprint than normal meta-programming.

http://groovy.codehaus.org/api/groovy/lang/ExpandoMetaClass.html#enableGlobally()

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