R允许引用类成为引用类的成员

Question

我试图让“class1”成为“class2”的元素。但是当“class1”具有initialize()函数时，我收到以下错误：

class1 <-
  setRefClass(
    'class1',
    fields = list(attribute1 = 'character'),
    methods = list(
    initialize = function(a){
      attribute1 <<- a
    }
   )
  )

class2 <- 
  setRefClass(
    'class2',
    fields = list(attribute2 = 'class1')
  )

  

.Object $ initialize（...）中的错误：    参数“a”缺失，没有默认值

Answer 1

为initialize方法提供默认值：

class1 <-
  setRefClass(
    'class1',
    fields = list(attribute1 = 'character'),
    methods = list(
      initialize = function(a = NA_character_){
        attribute1 <<- a
      }
    )
  )

class2 <- 
  setRefClass(
    'class2',
    fields = list(attribute2 = 'class1')
  )
test <- class2()
> test
Reference class object of class "class2"
Field "attribute2":
  Reference class object of class "class1"
Field "attribute1":
  [1] NA