För många klasser

Objektorienterad programmering med S3 och R6 i R

Richie Cotton

Data Evangelist at DataCamp

x <- c(1, 3, 6, 10, 15)

class(x) <- c(
  "triangular_numbers", "natural_numbers", "numeric"
)

is.numeric(x)

TRUE

is.triangular_numbers(x)

Error: could not find function "is.triangular_numbers"

inherits(x, "triangular_numbers")

TRUE

inherits(x, "natural_numbers")

TRUE

inherits(x, "numeric")

TRUE

what_am_i <- function(x, ...) {
  UseMethod("what_am_i")
}

what_am_i.triangular_numbers <- function(x, ...) {
  message("I'm triangular numbers")
  NextMethod("what_am_i")
}

what_am_i.natural_numbers <- function(x, ...) {
  message("I'm natural numbers")
  NextMethod("what_am_i")
}

what_am_i.numeric <- function(x, ...) {
  message("I'm numeric")
}

what_am_i(x)

I'm triangular numbers
I'm natural numbers
I'm numeric

ch2_4-too-much-class.017.png

what_am_i(x)

I'm triangular numbers
I'm natural numbers
I'm numeric

ch2_4-too-much-class.018.png

what_am_i(x)

I'm triangular numbers
I'm natural numbers
I'm numeric

ch2_4-too-much-class.019.png

what_am_i(x)

I'm triangular numbers
I'm natural numbers
I'm numeric

ch2_4-too-much-class.020.png

Sammanfattning

Objektorienterad programmering med S3 och R6 i R