R，R6，从R6Generator对象获取完整的类名 [英] R, R6, Get Full Class Name from R6Generator Object

问题描述

在R6中，如何在不创建生成器对象实例的情况下获取类继承的完整列表？

In R6, How can I get the full list of class inheritances, without creating instances of the generator objects?

请考虑以下内容：

A = R6::R6Class("Base",NULL)
B = R6::R6Class("Top",inherit = A)
class(B)     #Returns 'R6ClassGenerator'
B$classname  #Returns 'Top' 

我想要的是 c（'Top'，'Base'，'R6'）

换句话说，在现实世界中， class（B $ new（））

In other words, what would otherwise be returned by class(B$new())

将返回什么，我有一组复杂的继承，而且初始化程序有很多参数，有些没有默认值，所以我试图避免实例化一个新对象以获得此信息。

In the real world, I have a complex set of inheritances, and, initializers with many arguments, some without default values, so I am trying to avoid instantiating a new object in order to obtain this information.

推荐答案

没有一种内置方法来查找B继承的所有类而无需调用 B $ new（） 。这是因为继承是在实例化对象时确定的，而不是在创建类时确定的。一个类（AKA生成器对象）知道它所继承的类的 name ，但是仅在实例化对象时才对该名称进行评估。

There isn't a built-in way to find all the classes that B inherits without calling B$new(). This is because inheritance is determined when objects are instantiated, not when the classes are created. A class (AKA generator object) knows the name of the class it inherits from, but that name is evaluated only when objects are instantiated.

您可以执行以下操作来找到继承链，但这使用了一些将来可能会更改的内部API（尽管它们可能不会更改）：

You could do something like this to find the inheritance chain, but this uses some internal APIs that could possibly change in the future (although they probably won't):

findClasses <- function(x) {
  if (is.null(x))
    return(NULL)
  parent <- x$get_inherit()
  c(x$classname, findClasses(parent))
}

A <- R6::R6Class("Base",NULL)
B <- R6::R6Class("Middle", inherit = A)
C <- R6::R6Class("Top", inherit = B)
findClasses(C)
#> [1] "Top"    "Middle" "Base"  

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