我在 R6 类中使用活动绑定在分配给字段之前检查值。我以为我可以使用闭包来生成如下绑定,但这不起作用。
绑定没有以我期望的方式进行评估(完全?),因为错误显示了闭包的name
参数。我错过了什么?
library(R6)
library(pryr)
# pass a field name to create its binding
generate_binding <- function(name) {
function(value) {
if (!missing(value) && length(value) > 0) {
private$name <- value
}
private$name
}
}
bind_x = generate_binding(x_)
# created as intended:
unenclose(bind_x)
# function (value)
# {
# if (!missing(value) && length(value) > 0) {
# private$x_ <- value
# }
# private$x_
# }
MyClass <- R6::R6Class("MyClass",
private = list(
x_ = NULL
),
active = list(
x = bind_x
),
)
my_class_instance <- MyClass$new()
my_class_instance$x <- "foo"
# Error in private$name <- value :
# cannot add bindings to a locked environment