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daniel schnaider

2013-Nov-09 14:31 UTC

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

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<-")})
    setReplaceMethod("CustomerID", "Account", function(obj,
id){
        obj@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]]

Simon Zehnder

2013-Nov-09 16:22 UTC

head link

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

If you want to set a slot you have to refer to it:

ac at CustomerID <- ?54321? 

or you use your setter:

ac <- CustomerID(ac, ?54321?)

What you did was creating a new symbol CustomerID referring to the String
?54321?
CustomerID <- ?54321?
CustomerID
[1] ?54321?

Best

Simon

On 09 Nov 2013, at 15:31, daniel schnaider <dschnaider at gmail.com>
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<-")})
>    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]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Martin Morgan

2013-Nov-09 18:20 UTC

head link

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

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]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Computational Biology / Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N.
PO Box 19024 Seattle, WA 98109

Location: Arnold Building M1 B861
Phone: (206) 667-2793

Hadley Wickham

2013-Nov-10 07:31 UTC

head link

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

Modelling a mutable entity, i.e. an account, is really a perfect
example of when to use reference classes.  You might find the examples
on http://adv-r.had.co.nz/OO-essentials.html give you a better feel
for the strengths and weaknesses of R's different OO systems.

Hadley

On Sat, Nov 9, 2013 at 9:31 AM, daniel schnaider <dschnaider at gmail.com>
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<-")})
>     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]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.


-- 
Chief Scientist, RStudio
http://had.co.nz/

R help - Nov 2013 - S4; Setter function is not chaning slot value as expected

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

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

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

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