恢复R6对象

Question

假设我有一个简单的抽象R6类。

myClass <- R6::R6Class(
  classname = "myClass",
  public = list(
    save = function(path) {
      saveRDS(self, path)
    },
    load = function(path) {
      object <- readRDS(path)
      self <- object
      lockEnvironment(self)
      invisible(self)
    }
  )
)

然后我有个孩子课做一些事情

myChildClass <- R6::R6Class(
  classname = "myChildClass",
  inherit = myClass,
  lock_objects = FALSE,
  public = list(
    initialize = function(x) {
      private$x <- x
    },
    addOne = function() {
      private$x <- private$x + 1
      private$x
    }
  ),
  private = list(x = NA_real_)
)

我想要做的是能够保存我创建的类，然后在以后恢复它。

tmp <- myChildClass$new(x = 10)
tmp$addOne()
tmp$addOne()
tmpFile <- tempfile()
tmp$save(tmpFile)
new <- myClass$new()
new$load(tmpFile)
new
# <myClass>
#   Public:
#     clone: function (deep = FALSE)
#     load: function (path)
#     save: function (path)

我遇到的问题是，由于某种原因，当我们调用self时，实际上并没有更新$load()。如果我调试这个方法，我会发现它确实被覆盖了，但是对象new仍然返回初始的myClass对象，而没有加载的更改。唯一的方法，我似乎可以让它做我想做的是通过重新分配输出(显然)。

new <- myClass$new()
new <- new$load(tmpFile)
new
# <myChildClass>
#   Inherits from: <myClass>
#   Public:
#     addOne: function ()
#     clone: function (deep = FALSE) 
#     initialize: function (x)
#     load: function (path)
#     save: function (path)
#   Private:
#     x: 12

现在我明白了，我可以只使用readRDS()并完成它，但是我希望它是可链接的，因此尝试将它放在一个方法中。

Answer 1

活动绑定可用于直接调用load。

parent <- R6::R6Class(
    classname = "parent",
    public = list(
        # update path if supplied in new()
        initialize = function(path = NULL) if(!is.null(path)) self$path <- path,
        path = NULL,
        save = function(path) {
            saveRDS(self, path)
        },
        load = function(path) {
            object <- readRDS(path)
            self <- object
            lockEnvironment(self)
            invisible(self)
        }
    ),
    active = list(
        file = function() self <- self$load(self$path) # computed at each access
    )
)
child <- R6::R6Class(
    classname = "child",
    inherit = parent,
    lock_objects = FALSE,
    public = list(
        initialize = function(x) {
            private$x <- x
        },
        addOne = function() {
            private$x <- private$x + 1
            private$x
        }
    ),
    private = list(x = NA_real_)
)

tmp1 <- child$new(x = 10)
tmp1$addOne() # 11
tmpFile <- tempfile() #tmp nr 1
tmp1$save(tmpFile)

tmp2 <- parent$new(tmpFile)$file
tmp2$addOne() # 12
tmpFile2 <- tempfile()
tmp2$save(tmpFile2)

tmp3 <- parent$new(tmpFile2)$file
tmp3

#> <child>
#>   Inherits from: <parent>
#>   Public:
#>     addOne: function () 
#>     clone: function (deep = FALSE) 
#>     file: active binding
#>     initialize: function (x) 
#>     load: function (path) 
#>     path: NULL
#>     save: function (path) 
#>   Private:
#>     x: 12

这样，新的父级就可以放在链中。

parent$new(tmpFile2)$file$addOne()
[1] 13

以及来自?makeActiveBinding的相关警告

当前，在包安装期间没有保留活动绑定，但是可以在.onLoad中创建它们。