Fields containing reference objects - unwanted side effect

[jangorecki]

Using introduction vignette example:

library(R6)
e <- data.frame(a=1,b=2) # my BIG DATA

SimpleClass <- R6Class(
    classname = "SimpleClass",
    public = list(x = NULL)
)
NonSharedField <- R6Class(
    classname = "NonSharedField",
    public = list(
        e = NULL,
        initialize = function() e <<- SimpleClass$new()
    )
)

n1 <- NonSharedField$new()
n1$e$x <- 1

n2 <- NonSharedField$new()
n2$e$x <- 2

# n2$e$x does not affect n1$e$x
n1$e$x
# [1] 1

e
#<SimpleClass>
#  Public:
#    x:

My variable e has gone.

It seems that I can safely rm(e) from my global env and both classes will still works. But polluting the global env, potentially wiping out important variable is an issue IMO. Could it be addressed somehow? For me this is not a big issue, but I'm developing package which uses R6 and non shared fields and user of my package may not be aware of the risk.

[gluc]

Why are you assigning e <<- SimpleClass$new() globally in the constructor? That overwrites your global e.

[wch]

@jangorecki If you want to use <<- assignment in R6 classes, you need to use portable=FALSE. Otherwise, with portable=TRUE (which is the default) you'd need to do self$e <- SimpleClass$new().

See this section of the intro vignette for more information: http://cran.r-project.org/web/packages/R6/vignettes/Introduction.html#using-self-and--

[jangorecki]

@gluc as this is a recommended way from vignette to use reference objects from R6 and not sharing them. @wch so the only way to use reference object and not sharing that object is making portable=FALSE, is that correct? It might be worth to mention that in vignette then.

[wch]

No, you can use portable=TRUE and self$e <- SimpleClass$new().

[wch]

I just realized one reason this might be confusing. R does something weird and surprising when n1$e is NULL, and you assign n1$e$x <- 1: it turns n1$e into a list.

library(R6)
NonSharedField <- R6Class(
    classname = "NonSharedField",
    public = list(
        e = NULL
    )
)

n1 <- NonSharedField$new()
n1$e
# NULL

n1$e$x <- 1
str(n1$e)
# List of 1
#  $ x: num 1

But the advice remains the same: make it portable and use self.

[jangorecki]

Thanks for your comments. I don't know why when I tried to use self$e <- SimpleClass$new() in initialize I was ending up with shared object of SimpleClass. I must made some stupid mistake because now when I tried the way you describe it works like a charm. Thanks again! Still the vignette for using non-shared objects within R6 could mention self$ <- way, not only <<-.

[wch]

@jangorecki Ah, I didn't realize that your code was taken directly from the vignette! Sorry about that. That's definitely a bug in the vignette, and I'll fix it soon.

[jangorecki]

I'm glad there is at least some constructive input from that ticket. Thanks for great pkg dev!