CODEWITHSUNDEEP
roop
José Carlos
José Carlos

Reputation: 2922

R: How to modify values of slots?

I'm newbie in R and I have defined an object with one method called "show". In this method I modify the value of a slot and then I print to show its value. The value is correct.

method(show)

setMethod("show", "menu", function(object){
  while (TRUE){
    #Clean console
    cat("\014")
    cat("COMPARATIVA ENTRE EQUIPOS DE LA MISMA COMPETICION\n")
    cat("-------------------------------------------------\n\n")
    cat("1. Comparativa entre clubes de Liga DIA\n")
    cat("2. Comparativa entre clubes de Liga Femenina 2 - Grupo 'A'\n")
    cat("3. Comparativa entre clubes de Liga Femenina 2 - Grupo 'B'\n")
    cat("0. Salir\n\n")
    option <- readline("Selecciona opción: ")
    option <- suppressWarnings(as.numeric(option))
    if (!is.na(option)){
      if (option == 1){
        object@competition <- 14
      }
      if (option == 2){
        object@competition <- 22
      }
      if (option == 3){
        object@competition <- 23
      }
      print(object@competition)
      readline("Espera ...")
      if (option == 0)
        break
    }else{
      readline("No es un número. Pulsa una tecla para introducir otra opción.")
    }
  }  
})

But If I try to access to the slot outside this method I've got the initial value.

x <- menu(competition=0, stats=0)
x
print(x@competition)

When I call "x" I'm calling the "show" method too and inside of them I give a value to "competition" different to 0. But, later, when I try to print the value with print(x@competition) I've got like result 0.

> print(x@competition)
[1] 0

I would like to get the value assigned inside "show" method but I've got the value when I create the object. How can I modify the value of the slot correctly?

Upvotes: 0

Views: 371

Answers (1)

niko
niko

Reputation: 5281

Okay so here are a couple of lines that helped for me:

myFun <- function(object) 0
setGeneric("myFun")
setClass("myClass", slots = c("competition", "stats"))

I then proceed with your code (slightly modified the the setMethod):

setMethod("myFun", "myClass", function(object){
  while (TRUE){
    #Clean console
    cat("\014")
    cat("COMPARATIVA ENTRE EQUIPOS DE LA MISMA COMPETICION\n")
    cat("-------------------------------------------------\n\n")
    cat("1. Comparativa entre clubes de Liga DIA\n")
    cat("2. Comparativa entre clubes de Liga Femenina 2 - Grupo 'A'\n")
    cat("3. Comparativa entre clubes de Liga Femenina 2 - Grupo 'B'\n")
    cat("0. Salir\n\n")
    option <- readline("Selecciona opción: ")
    option <- suppressWarnings(as.numeric(option))
    if (!is.na(option)){
      if (option == 1){
        object@competition <- 14
        break
      }
      if (option == 2){
        object@competition <- 22
        break
      }
      if (option == 3){
        object@competition <- 23
        break
      }
      print(object@competition)
      readline("Espera ...")
      if (option == 0)
        break
    }else{
      readline("No es un número. Pulsa una tecla para introducir otra opción.")
    }
  }
return(object)  
})

Here is my output:

x <- new("myClass", competition = 0, stats = 0)
# printing just x yields:
An object of class "myClass"
Slot "competition":
[1] 0

Slot "stats":
[1] 0

# Here is what myFun(x) yields:
COMPARATIVA ENTRE EQUIPOS DE LA MISMA COMPETICION
-------------------------------------------------

1. Comparativa entre clubes de Liga DIA 
2. Comparativa entre clubes de Liga Femenina 2 - Grupo 'A'
3. Comparativa entre clubes de Liga Femenina 2 - Grupo 'B'
0. Salir

Selecciona opción:
# hits 1
An object of class "myClass"
Slot "competition":
[1] 14

Slot "stats":
[1] 0

Now setting y <- myFun(x), we obtain (again hitting 1 in the console):

> print(y@competition)
[1] 14

Upvotes: 1

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