R6类嵌套函数访问self报错，求无需升级R6的解决方案

你遇到的问题本质是：嵌套在普通list中的函数不属于R6类的方法成员，R6只会给直接定义在public/private等区块内的方法自动注入self对象，普通list里的函数没有这个上下文绑定，所以调用时找不到self。以下是无需升级R6的替代解决方案：

方案一：用R6类层级替代嵌套list #

把每个层级的嵌套结构都定义成独立的R6类，初始化时传递主Person实例，保持上下文关联：

library(R6)

# 定义底层R6类，接收主Person实例
Level3 <- R6Class("Level3",
  public = list(
    person = NULL,
    method = function() {
      print(self$person$name)
    },
    initialize = function(person) {
      self$person = person
    }
  )
)

Level2 <- R6Class("Level2",
  public = list(
    person = NULL,
    level3 = NULL,
    initialize = function(person) {
      self$person = person
      self$level3 = Level3$new(person)
    }
  )
)

Level1 <- R6Class("Level1",
  public = list(
    person = NULL,
    level2 = NULL,
    initialize = function(person) {
      self$person = person
      self$level2 = Level2$new(person)
    }
  )
)

# 主Person类，初始化时创建层级实例
Person <- R6Class("Person",
  public = list(
    name = NULL,
    level1 = NULL,
    initialize = function(name) {
      self$name = name
      self$level1 = Level1$new(self)
    }
  )
)

jay = Person$new(name = "Jay")
jay$level1$level2$level3$method()

方案二：手动给嵌套函数注入self环境 #

在Person的initialize方法中，修改嵌套函数的运行环境，手动添加self变量：

library(R6)

Person <- R6Class("Person",
  public = list(
    name = NULL,
    level1 = list(
      level2 = list(
        level3 = list(
          method = function() {
            print(self$name)
          }
        )
      )
    ),
    initialize = function(name) {
      self$name = name
      # 用base R修改函数环境，注入self
      target_func <- self$level1$level2$level3$method
      new_env <- new.env(parent = environment(target_func))
      new_env$self <- self
      environment(target_func) <- new_env
    }
  )
)

jay = Person$new(name = "Jay")
jay$level1$level2$level3$method()

若已安装rlang包，可使用更简洁的环境修改方式：

environment(self$level1$level2$level3$method) <- rlang::env(
  parent = environment(self$level1$level2$level3$method),
  self = self
)

方案三：在initialize中动态构建嵌套结构 #

把嵌套的list和函数移到initialize方法中定义，利用闭包特性自动捕获当前的self：

library(R6)

Person <- R6Class("Person",
  public = list(
    name = NULL,
    level1 = NULL,
    initialize = function(name) {
      self$name = name
      # 在initialize内部构建嵌套结构，函数自动捕获self上下文
      self$level1 <- list(
        level2 = list(
          level3 = list(
            method = function() {
              print(self$name)
            }
          )
        )
      )
    }
  )
)

jay = Person$new(name = "Jay")
jay$level1$level2$level3$method()

内容的提问来源于stack exchange，提问作者irudnyts