On 27/03/2021 10:16 a.m., Jiefei Wang wrote:
Hi all,
I'm trying to get the field value of a reference object by the field name,
but the dollar symbol behaves quite unusual. See example below
*.foo <- setRefClass( "foo", fields = list( a = "integer"
))x <- .foo$new(a=1L)## This is OKx$a## This is OK`$`(x, "a")## But this is
not OKi <- "a"`$`(x, i)*
This is really hard to read. Please post it again, but don't use HTML.
Duncan Murdoch
For the last line of code I get this error
*Error in envRefInferField(x, what, getClass(class(x)), selfEnv) : ‘i’ is
not a valid field or method name for reference class “foo”*
It looks like when calling the dollar symbol using the function format, it
treats the input argument as a character literal and does not evaluate it
inside the function. I know we have the function `field` to get the slot
variable, but I wonder if this is designed on purpose as the above example
works for both list and S4 system.
Best,
Jiefei
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