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#### Testing UseMethod() and even more NextMethod()
#### --------------------
#### i.e., S3 methods *only*. For S4, see reg-S4.R
## ~~~~~~~~
###-- Group methods
## previous versions used print() and hit an auto-printing bug.
### Arithmetic "Ops" :
">.bar" <- function(...) {cat("using >.bar\n"); FALSE}
">.foo" <- function(...) {cat("using >.foo\n"); TRUE}
Ops.foo <- function(...) {
cat("using Ops.foo\n")
NextMethod()
}
Ops.bar <- function(...) {
cat("using Ops.bar\n")
TRUE
}
x <- 2:4 ; class(x) <- c("foo", "bar")
y <- 4:2 ; class(y) <- c("bar", "foo")
## The next 4 give a warning each about incompatible methods:
x > y
y < x # should be the same (warning msg not, however)
x == y
x <= y
x > 3 ##[1] ">.foo"
rm(list=">.foo")
x > 3 #-> "Ops.foo" and ">.bar"
### ------------ was ./mode-methods.R till R ver. 1.0.x ----------------
###-- Using Method Dispatch on "mode" etc :
## Tests S3 dispatch with the class attr forced to be data.class
## Not very relevant when S4 methods are around, but kept for historical interest
abc <- function(x, ...) {
cat("abc: Before dispatching; x has class `", class(x), "':", sep="")
str(x)
UseMethod("abc", x) ## UseMethod("abc") (as in S) fails
}
abc.default <- function(x, ...) sys.call()
"abc.(" <- function(x)
cat("'(' method of abc:", deparse(sys.call(sys.parent())),"\n")
abc.expression <- function(x)
cat("'expression' method of abc:", deparse(sys.call(sys.parent())),"\n")
abc(1)
e0 <- expression((x))
e1 <- expression(sin(x))
abc(e0)
abc(e1)
abc(e0[[1]])
abc(e1[[1]])
## Some tests for `nameOfClass()`, called from inherits()
ClassX <- structure(list(), name = "ClassX",
class = c("S3pp_class", "S3pp_object"))
classx_instance <- structure(list(), class = c("ClassX", "S3pp_object"))
nameOfClass.S3pp_class <- function(x) attr(x, "name", TRUE)
nameOfClass.foo <- function(x) "bar"
stopifnot(exprs = {
inherits(classx_instance, "ClassX")
inherits(classx_instance, ClassX)
## ignore class on a character object
isTRUE(inherits(1, structure("numeric", class = "foo")))
## make sure class is nor evaluated in calling nameOfClass
isFALSE(inherits(1, structure(quote(stop("should not be evaluated")),
class = "foo")))
})
## Some tests for `@` dispatching
## make sure that
## - `@` evals the first args only once,
## - doesn't dispatch for S4
## - works on `.Data` even for nonS4 objects
x <- structure(list(), class = "foo", prop1 = 'prop1val')
registerS3method("@", "foo",
function(x, name) {
stopifnot(typeof(name) == "character", length(name) == 1L)
cat(sprintf("called `@.foo`(x = %s, name = '%s')\n",
deparse1(substitute(x), "\n"), name))
attr(x, name, TRUE)
}
)
x@prop1
abc <- x
abc@prop1
{
cat("new x\n")
structure(list(), class = "foo", prop1 = 'prop1val')
}@prop1
makeActiveBinding("ax", function(x) {
cat("evaluating ax\n")
get("x", envir = parent.frame())
}, environment())
ax@prop1
stopifnot(exprs = {
identical( x@prop1, "prop1val")
identical(ax@prop1, "prop1val")
identical(letters@.Data, letters)
})
try(letters@foo) # error
# doesn't dispatch for S4
setClass("Person",
slots = c(
name = "character",
age = "numeric"
)
)
`@.Person` <- function(x, name) {
stop("called @.Person()\n")
}
p <- new("Person", name = "Who", age = -1)
stopifnot(p@name == "Who")
## Some tests for `chooseOpsMethod()`, called from C DispatchGroup() when
## 2 methods are found
foo_obj <- structure(1, class = "foo")
bar_obj <- structure(1, class = "bar")
`+.foo` <- function(e1, e2) "foo"
`+.bar` <- function(e1, e2) "bar"
invisible(foo_obj + bar_obj) # Warning: Incompatible methods
chooseOpsMethod.bar <- function(x, y, mx, my, cl, reverse) TRUE
stopifnot(exprs = {
identical(foo_obj + bar_obj, "bar")
identical(bar_obj + foo_obj, "bar")
})
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