R refClass Methods - r

Question

I am using R refClass example below.
Person = setRefClass("Person",fields = list(name = "character", age = "numeric")
) ## Person = setRefClass("Person",
Person$methods = list(
increaseAge <- function(howMuch){
age = age + howMuch
}
)
When I store this program in a file called Person.R and source it, it does not show any errors. Now I instantiate a new object.
p = new("Person",name="sachin",age=40)
And I try to invoke the method increaseAge, using p$increaseAge(40), and it shows the following error
Error in envRefInferField(x, what, getClass(class(x)), selfEnv) :
"increaseAge" is not a valid field or method name for reference class "Person"
I cannot figure out why it says that the method increaseAge is not a valid method name when I have defined it.

Answer 1

To specify a method independent of class definition, invoke the methods() function on the generator. Also, use either <<- or .self$age = for the assignment.
Person$methods(increaseAge=function(howMuch) {
age <<- age + howMuch
## alterenatively, .self$age = age + howMuch or .self$age <- age + howMuch
})
Remember that R works best on vectors, so think of a Persons class (modeling columns) representing all the individuals in your study, rather than a collection of Person instances (modeling rows).

Answer 2

I get an error using your code. I would do something like this:
Person = setRefClass("Person",
fields = list(name = "character", age = "numeric"),
methods = list(
increaseAge = function(howMuch) age <<- age + howMuch
))
> p = new("Person",name="sachin",age=40)
> p$increaseAge(5)
> p$age
[1] 45