[R] S4; Setter function is not chaning slot value as expected

[Martin Morgan]

On 11/09/2013 06:31 AM, daniel schnaider wrote:
> It is my first time programming with S4 and I can't get the setter fuction
> to actually change the value of the slot created by the constructor.
>
> I guess it has to do with local copy, global copy, etc. of the variable -
> but, I could't find anything relevant in documentation.
>
> Tried to copy examples from the internet, but they had the same problem.
>
> # The code
>      setClass ("Account" ,
>                 representation (
>                 customer_id = "character",
>                 transactions = "matrix")
>      )
>
>
>      Account <- function(id, t) {
>              new("Account", customer_id = id, transactions = t)
>              }
>
>
>      setGeneric ("CustomerID<-", function(obj,
> id){standardGeneric("CustomerID<-")})

Replacement methods (in R in general) require that the final argument (the 
replacement value) be named 'value', so

     setGeneric("CustomerID<-",
         function(x, ..., value) standardGeneric("CustomerID"))

     setReplaceMethod("CustomerID", c("Account", "character"),
         function(x, ...., value)
     {
         x at customer_id <- value
         x
     })

use this as

    CustomerID(ac) <- "54321"


>      setReplaceMethod("CustomerID", "Account", function(obj, id){
>          obj at customer_id <- id
>          obj
>          })
>
>          ac <- Account("12345", matrix(c(1,2,3,4,5,6), ncol=2))
>          ac
>          CustomerID <- "54321"
>          ac
>
> #Output
>          > ac
>          An object of class "Account"
>          Slot "customer_id":
>          [1] "12345"
>
>          Slot "transactions":
>               [,1] [,2]
>          [1,]    1    4
>          [2,]    2    5
>          [3,]    3    6
>
> # CustomerID is value has changed to 54321, but as you can see it does't
>          > CustomerID <- "54321"

>          > ac
>          An object of class "Account"
>          Slot "customer_id":
>          [1] "12345"
>
>          Slot "transactions":
>               [,1] [,2]
>          [1,]    1    4
>          [2,]    2    5
>          [3,]    3    6
>
>
> Help!
>
> 	[[alternative HTML version deleted]]
>
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>


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