[英]Inside R6 class definition: 'object not found' (or: how to define 'local' objects in R6 classes)
I want to define an R6 class that sets up, updates and closes a progress bar.我想定义一个设置、更新和关闭进度条的 R6 class。 For these 3 tasks, I have 3 functions.
对于这 3 个任务,我有 3 个功能。 The first,
setup_progressbar()
, calls R
's txtProgressbar()
which returns an object (say, pb
) which needs to be passed on to the second and third functions, update_progressbar()
and close_progressbar()
.第一个
setup_progressbar()
调用R
的txtProgressbar()
,它返回一个 object (比如pb
),它需要传递给第二个和第三个函数update_progressbar()
和close_progressbar()
。 But the object pb
is not found by the latter two functions.但是后两个函数没有找到 object
pb
。
library(R6)
myprogressbar <- R6Class("my_progress_bar",
public = list(
n = numeric(1),
initialize = function(n) {
stopifnot(n >= 1)
self$n <- n
},
setup_progressbar = function() {
pb <- txtProgressBar(max = self$n)
},
update_progressbar = function(i) {
setTxtProgressBar(pb, i)
},
close_progressbar = function () {
close(pb)
cat("\n")
}
))
mypb <- myprogressbar$new(10)
mypb$setup_progressbar()
mypb$update_progressbar(3) # Error in setTxtProgressBar(pb, i) : object 'pb' not found
I tried to add pb
to self
in the hope it would be found, but then I obtain "cannot add bindings to a locked environment"
.我试图将
pb
添加到self
希望它会被发现,但后来我得到"cannot add bindings to a locked environment"
。
Note: In my actual (non-minimal) example, the i
is found/provided/visible, so that's not an additional problem (most likely this is just a problem in the above minimal working example once fixed beyond the 'pb' not found
error).注意:在我的实际(非最小)示例中,
i
被发现/提供/可见,所以这不是一个额外的问题(很可能这只是上述最小工作示例中的一个问题,一旦修复超出了'pb' not found
错误)。
The following works:以下作品:
library(R6)
myprogressbar <- R6Class("my_progress_bar",
public = list(
n = numeric(1),
pb = NULL, # provide as argument
initialize = function(n, pb = NULL) { # provide with default so that $new() doesn't require 'pb'
stopifnot(n >= 1)
self$n <- n
},
setup_progressbar = function() {
self$pb <- txtProgressBar(max = self$n)
},
update_progressbar = function(i) {
setTxtProgressBar(self$pb, i)
},
close_progressbar = function () {
close(self$pb)
cat("\n")
}
))
mypb <- myprogressbar$new(10)
mypb$setup_progressbar()
mypb$update_progressbar(3)
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