CODEWITHSUNDEEP
rr-s4slots
Claas-Thido Pfaff
Claas-Thido Pfaff

Reputation: 95

Dynamically create nested s4 class slot names and assign values in R

I try to assign values to nested s4 classes slots in R in a dynamic way. What I have so far is the code below. I create the following nested classes ending with nested slot of type numeric.

setClass('slot', slots = c(slot = 'numeric'))
setClass('object', slots = c(slot = 'slot'))
object = new('object')
object@slot@slot

Typical assignement works as expected:

object@slot@slot = 1

or:

slot(object@slot, "slot") <- 1

What I want do to however is a dynamic creation of the slot names for the assignment for example with paste from a vector like e.g. 

slot_path = c("object", "slot", "slot")

Using eval and parse does the trick to convert the string into the object and shows me the object or in that case here the slot of the object. 

eval(parse(text = paste(slot_path, collapse="@")))

However assigning values to that kind of construct seems not to work as expected. 

eval(parse(text = paste(slot_path, collapse="@"))) <- 2

Gives me the error that says:

Error in file(filename, "r") : cannot open the connection.

If I paste the path manually like that:

eval(parse(text = "object@slot@slot")) <- 1

I get the error that says:

Error in eval(parse(text = "object@slot@slot")) <- 1 : target of assignment expands to non-language object

Trying to assign with the assign() function also does not do the trick. The call below:

assign(x = slot(eval(parse(text = "object@slot")), "slot"), value = 1)

Gives me the error:

Error in assign(x = slot(eval(parse(text = "object@slot")), "slot"), value = 1) : invalid first argument

Any help with that would be appreciated.

Upvotes: 3

Views: 1158

Answers (1)

Claas-Thido Pfaff
Claas-Thido Pfaff

Reputation: 95

I found a solution:

For numeric:

eval(parse(text = eval(expression(paste(pasted_slot_path, "<-", value)))))

For character: 

value = sprintf('"%s"',value)
    eval(parse(text = eval(expression(paste(pasted_slot_path, "<-", value)))))

Upvotes: 1

Related Questions