tests/callHooks.R

In R.utils: Various Programming Utilities

library("R.utils")

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# Example 1
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# First, clean up if called more than once
setHook("myFunction.onEnter", NULL, action="replace")
setHook("myFunction.onExit", NULL, action="replace")

runConference <- function(...) {
  callHooks("myFunction.onEnter")
  cat("Speaker A: Hello there...\n")
  callHooks("myFunction.onExit")
}

setHook("myFunction.onEnter", function(...) {
  cat("Chair: Welcome to our conference.\n")
})

setHook("myFunction.onEnter", function(...) {
  cat("Chair: Please welcome Speaker A!\n")
})

setHook("myFunction.onExit", function(...) {
  cat("Chair: Please thanks Speaker A!\n")
})

runConference()


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# Example 2
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setHook("randomNumber", NULL, action="replace")
setHook("randomNumber", rnorm)      # By function
setHook("randomNumber", "rexp")     # By name
setHook("randomNumber", "runiff")   # Non-existing name
setHook("randomNumber", .GlobalEnv) # Not a function

res <- callHooks("randomNumber", n=1, removeCalledHooks=TRUE)
str(res)
cat("Number of hooks: ", length(res), "\n")
isErroneous <- unlist(lapply(res, FUN=function(x) !is.null(x$exception)))
cat("Erroneous hooks: ", sum(isErroneous), "\n")



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# Exception handling
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res <- try(callHooks(character(0L)), silent=TRUE)
stopifnot(inherits(res, "try-error"))

res <- try(callHooks(c("a", "b")), silent=TRUE)
stopifnot(inherits(res, "try-error"))